[media] dw2102: fix compile warnings

media_build/v4l/dw2102.c:151:13: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dw2102.c:224:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dw2102.c:279:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dw2102.c:352:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dw2102.c:435:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dw2102.c:499:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>