[media] media: davinci: vpbe: fix layer availability for NV12 format

For NV12 format, even if display data is single image,
both VIDWIN0 and VIDWIN1 parameters must be used. The start
address of Y data plane and C data plane is configured in
VIDEOWIN0ADH/L and VIDEOWIN1ADH/L respectively.
cuurently only one layer was requested, which is suffice
for yuv422, but for yuv420(NV12) two layers are required and
fix the same by requesting for other layer if pix fmt is NV12
during set_fmt.

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@redhat.com>