media: si470x-i2c: fix possible memory leak in si470x_i2c_probe()

n the 'radio->hdl.error' error handling, ctrl handler allocated by
v4l2_ctrl_new_std() does not released, and caused memory leak as
follows:

unreferenced object 0xffff888033d54200 (size 256):
  comm "i2c-si470x-19", pid 909, jiffies 4294914203 (age 8.072s)
  hex dump (first 32 bytes):
    e8 69 11 03 80 88 ff ff 00 46 d5 33 80 88 ff ff  .i.......F.3....
    10 42 d5 33 80 88 ff ff 10 42 d5 33 80 88 ff ff  .B.3.....B.3....
  backtrace:
    [<00000000086bd4ed>] __kmalloc_node+0x1eb/0x360
    [<00000000bdb68871>] kvmalloc_node+0x66/0x120
    [<00000000fac74e4c>] v4l2_ctrl_new+0x7b9/0x1c60 [videodev]
    [<00000000693bf940>] v4l2_ctrl_new_std+0x19b/0x270 [videodev]
    [<00000000c0cb91bc>] si470x_i2c_probe+0x2d3/0x9a0 [radio_si470x_i2c]
    [<0000000056a6f01f>] i2c_device_probe+0x4d8/0xbe0

Fix the error handling path to avoid memory leak.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 8c081b6f ("media: radio: Critical v4l2 registration...")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>