media: venus: core, venc, vdec: Fix probe dependency error

Commit aaaa93ed ("media] media: venus: venc: add video encoder files")
is the last in a series of three commits to add core.c vdec.c and venc.c
adding core, encoder and decoder.

The encoder and decoder check for core drvdata as set and return -EPROBE_DEFER
if it has not been set, however both the encoder and decoder rely on
core.v4l2_dev as valid.

core.v4l2_dev will not be valid until v4l2_device_register() has completed
in core.c's probe().

Normally this is never seen however, Dmitry reported the following
backtrace when compiling drivers and firmware directly into a kernel image.

[    5.259968] Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
[    5.269850] sd 0:0:0:3: [sdd] Optimal transfer size 524288 bytes
[    5.275505] Workqueue: events deferred_probe_work_func
[    5.275513] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)
[    5.441211] usb 2-1: new SuperSpeedPlus Gen 2 USB device number 2 using xhci-hcd
[    5.442486] pc : refcount_warn_saturate+0x140/0x148
[    5.493756] hub 2-1:1.0: USB hub found
[    5.496266] lr : refcount_warn_saturate+0x140/0x148
[    5.500982] hub 2-1:1.0: 4 ports detected
[    5.503440] sp : ffff80001067b730
[    5.503442] x29: ffff80001067b730
[    5.592660] usb 1-1: new high-speed USB device number 2 using xhci-hcd
[    5.598478] x28: ffff6c6bc1c379b8
[    5.598480] x27: ffffa5c673852960 x26: ffffa5c673852000
[    5.598484] x25: ffff6c6bc1c37800 x24: 0000000000000001
[    5.810652] x23: 0000000000000000 x22: ffffa5c673bc7118
[    5.813777] hub 1-1:1.0: USB hub found
[    5.816108] x21: ffffa5c674440000 x20: 0000000000000001
[    5.820846] hub 1-1:1.0: 4 ports detected
[    5.825415] x19: ffffa5c6744f4000 x18: ffffffffffffffff
[    5.825418] x17: 0000000000000000 x16: 0000000000000000
[    5.825421] x15: 00000a4810c193ba x14: 0000000000000000
[    5.825424] x13: 00000000000002b8 x12: 000000000000f20a
[    5.825427] x11: 000000000000f20a x10: 0000000000000038
[    5.845447] usb 2-1.1: new SuperSpeed Gen 1 USB device number 3 using xhci-hcd
[    5.845904]
[    5.845905] x9 : 0000000000000000 x8 : ffff6c6d36fae780
[    5.871208] x7 : ffff6c6d36faf240 x6 : 0000000000000000
[    5.876664] x5 : 0000000000000004 x4 : 0000000000000085
[    5.882121] x3 : 0000000000000119 x2 : ffffa5c6741ef478
[    5.887578] x1 : 3acbb3926faf5f00 x0 : 0000000000000000
[    5.893036] Call trace:
[    5.895551]  refcount_warn_saturate+0x140/0x148
[    5.900202]  __video_register_device+0x64c/0xd10
[    5.904944]  venc_probe+0xc4/0x148
[    5.908444]  platform_probe+0x68/0xe0
[    5.912210]  really_probe+0x118/0x3e0
[    5.915977]  driver_probe_device+0x5c/0xc0
[    5.920187]  __device_attach_driver+0x98/0xb8
[    5.924661]  bus_for_each_drv+0x68/0xd0
[    5.928604]  __device_attach+0xec/0x148
[    5.932547]  device_initial_probe+0x14/0x20
[    5.936845]  bus_probe_device+0x9c/0xa8
[    5.940788]  device_add+0x3e8/0x7c8
[    5.944376]  of_device_add+0x4c/0x60
[    5.948056]  of_platform_device_create_pdata+0xbc/0x140
[    5.953425]  of_platform_bus_create+0x17c/0x3c0
[    5.958078]  of_platform_populate+0x80/0x110
[    5.962463]  venus_probe+0x2ec/0x4d8
[    5.966143]  platform_probe+0x68/0xe0
[    5.969907]  really_probe+0x118/0x3e0
[    5.973674]  driver_probe_device+0x5c/0xc0
[    5.977882]  __device_attach_driver+0x98/0xb8
[    5.982356]  bus_for_each_drv+0x68/0xd0
[    5.986298]  __device_attach+0xec/0x148
[    5.990242]  device_initial_probe+0x14/0x20
[    5.994539]  bus_probe_device+0x9c/0xa8
[    5.998481]  deferred_probe_work_func+0x74/0xb0
[    6.003132]  process_one_work+0x1e8/0x360
[    6.007254]  worker_thread+0x208/0x478
[    6.011106]  kthread+0x150/0x158
[    6.014431]  ret_from_fork+0x10/0x30
[    6.018111] ---[ end trace f074246b1ecdb466 ]---

This patch fixes by

- Only setting drvdata after v4l2_device_register() completes
- Moving v4l2_device_register() so that suspend/reume in core::probe()
  stays as-is
- Changes pm_ops->core_function() to take struct venus_core not struct
  device
- Minimal rework of v4l2_device_*register in probe/remove

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>