media: doc: pixfmt-yuv: Move all luma-only YUV formats to common file

media: doc: pixfmt-yuv: Move all luma-only YUV formats to common file

Luma-only pixel formats are documented in separate files. This
duplicates information, as those formats share comon traits. Consolidate
them in a single file and describe them in a single table.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>