Move the lock/unlock to its own function. It makes the code cleaner and
cocci happier.

Fix the following cocci warning:
drivers/media/usb/go7007/go7007-i2c.c:125:1-7: preceding lock on line 61
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>