[media] media: davinci: vpbe: use fh handling provided by v4l

this patch converts the driver to use fh handling provided by the
v4l core instead of driver doing it.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>