drm/tegra: sor: Ensure regulators are disabled on teardown

The Tegra SOR driver uses the devm infrastructure to request regulators,
but enables them without registering them with the infrastructure.

This results in the following splat if probing fails for any odd resaon
(such as dependencies not being available):

[    8.974187] tegra-sor 15580000.sor: cannot get HDMI supply: -517
[    9.414403] tegra-sor 15580000.sor: failed to probe HDMI: -517
[    9.421240] ------------[ cut here ]------------
[    9.425879] WARNING: CPU: 1 PID: 164 at drivers/regulator/core.c:2089 _regulator_put.part.0+0x16c/0x174
[    9.435259] Modules linked in: tegra_drm(E+) cec(E) ahci_tegra(E) drm_kms_helper(E) drm(E) libahci_platform(E) libahci(E) max77620_regulator(E) xhci_tegra(E+) sdhci_tegra(E) xhci_hcd(E) libata(E) sdhci_pltfm(E) cqhci(E) fixed(E) usbcore(E) scsi_mod(E) sdhci(E) host1x(E)
[    9.459211] CPU: 1 PID: 164 Comm: systemd-udevd Tainted: G S    D W   E     5.9.0-rc7-00298-gf6337624c4fe #1980
[    9.469285] Hardware name: NVIDIA Jetson TX2 Developer Kit (DT)
[    9.475202] pstate: 80000005 (Nzcv daif -PAN -UAO BTYPE=--)
[    9.480784] pc : _regulator_put.part.0+0x16c/0x174
[    9.485581] lr : regulator_put+0x44/0x60
[    9.489501] sp : ffffffc011d837b0
[    9.492814] x29: ffffffc011d837b0 x28: ffffff81dd085900
[    9.498141] x27: ffffff81de1c8ec0 x26: ffffff81de1c8c10
[    9.503464] x25: ffffff81dd085800 x24: ffffffc008f2c6b0
[    9.508790] x23: ffffffc0117373f0 x22: 0000000000000005
[    9.514101] x21: ffffff81dd085900 x20: ffffffc01172b098
[    9.515822] ata1: SATA link down (SStatus 0 SControl 300)
[    9.519426] x19: ffffff81dd085100 x18: 0000000000000030
[    9.530122] x17: 0000000000000000 x16: 0000000000000000
[    9.535453] x15: 0000000000000000 x14: 000000000000038f
[    9.540777] x13: 0000000000000003 x12: 0000000000000040
[    9.546105] x11: ffffff81eb800000 x10: 0000000000000ae0
[    9.551417] x9 : ffffffc0106fea24 x8 : ffffff81de83e6c0
[    9.556728] x7 : 0000000000000018 x6 : 00000000000003c3
[    9.562064] x5 : 0000000000005660 x4 : 0000000000000000
[    9.567392] x3 : ffffffc01172b388 x2 : ffffff81de83db80
[    9.572702] x1 : 0000000000000000 x0 : 0000000000000001
[    9.578034] Call trace:
[    9.580494]  _regulator_put.part.0+0x16c/0x174
[    9.584940]  regulator_put+0x44/0x60
[    9.588522]  devm_regulator_release+0x20/0x2c
[    9.592885]  release_nodes+0x1c8/0x2c0
[    9.596636]  devres_release_all+0x44/0x6c
[    9.600649]  really_probe+0x1ec/0x504
[    9.604316]  driver_probe_device+0x100/0x170
[    9.608589]  device_driver_attach+0xcc/0xd4
[    9.612774]  __driver_attach+0xb0/0x17c
[    9.616614]  bus_for_each_dev+0x7c/0xd4
[    9.620450]  driver_attach+0x30/0x3c
[    9.624027]  bus_add_driver+0x154/0x250
[    9.627867]  driver_register+0x84/0x140
[    9.631719]  __platform_register_drivers+0xa0/0x180
[    9.636660]  host1x_drm_init+0x60/0x1000 [tegra_drm]
[    9.641629]  do_one_initcall+0x54/0x2d0
[    9.645490]  do_init_module+0x68/0x29c
[    9.649244]  load_module+0x2178/0x26c0
[    9.652997]  __do_sys_finit_module+0xb0/0x120
[    9.657356]  __arm64_sys_finit_module+0x2c/0x40
[    9.661902]  el0_svc_common.constprop.0+0x80/0x240
[    9.666701]  do_el0_svc+0x30/0xa0
[    9.670022]  el0_svc+0x18/0x50
[    9.673081]  el0_sync_handler+0x90/0x318
[    9.677006]  el0_sync+0x158/0x180
[    9.680324] ---[ end trace 90f6c89d62d85ff6 ]---

Instead, let's register a callback that will disable the regulators
on teardown. This allows for the removal of the .remove callbacks,
which are not needed anymore.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>