media: sun6i-csi: capture: Remove useless ret initialization

There is no particular need to assign ret when declaring it as
it will be assigned before there is any chance to return it.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>