media: i2c: imx477: Fix locking in imx477_init_controls()

The driver does not lock the imx477 mutex when calling
imx477_set_framing_limits(), leading to:

WARNING: CPU: 3 PID: 426 at drivers/media/v4l2-core/v4l2-ctrls-api.c:934 __v4l2_ctrl_modify_range+0x1a0/0x210 [
videodev]

Fix this by taking the lock.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>