media: ov7670: Remove useless use of a ret variable

Instead of assigning the return value to ret and then checking and
returning it, just return the value to the caller directly. The success
value is always 0.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>