media: davinci: don't override the error code

As warned by Coverity:
	CID 1415211 (#1 of 1): Unused value (UNUSED_VALUE)assigned_value:
	Assigning value -22 to ret here, but that stored value is
	overwritten before it can be used.

On all cases where the there's a goto 'unlock_out' or 'streamof',
ret was filled with a non-sero value. It toesn't make sense to override
such error code with a videobuf_streamoff() error.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>