media: davinci/vpfe_capture.c: drop unused format descriptions

Simplify vpfe_pixel_format to just contain the pixelformat and bpp fields.
All others are unused.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>