media: st-delta: Remove redundant assignment to ret

Variable ret is being assigned a value however the assignment is
never read, so this redundant assignment can be removed.

Clean up the following clang-analyzer warning:

drivers/media/platform/sti/delta/delta-v4l2.c:1010:4: warning: Value
stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>