[media] davinci: vpif_capture: fix default pixel format for BT.656/BT.1120 video

For both BT.656 and BT.1120 video, the pixel format
used by VPIF is Y/CbCr 4:2:2 in semi-planar format
(Luma in one plane and Chroma in another). This
corresponds to NV16 pixel format.

This is documented in section 36.2.3 of OMAP-L138
Technical Reference Manual, SPRUH77A.

The VPIF driver incorrectly sets the default format
to V4L2_PIX_FMT_YUV422P. Fix it.

Reported-by: Alejandro Hernandez <ajhernandez@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>