media: ov6650: fix smatch warning

Initialize ret to 0 to fix this smatch error:

drivers/media/i2c/ov6650.c:853 ov6650_video_probe() error: uninitialized symbol 'ret'.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>