[media] media: davinci: vpif_display: use v4l2_fh_open and vb2_fop_release
this patch adds support to use v4l2_fh_open() and vb2_fop_release,
which allows to drop driver specific struct vpif_fh, as this is handeled
by core. This patch also drops vpif_g/s_priority as this handeled
by core.