[media] doc-rst: Unify documentation of the 8-bit bayer formats

The other raw bayer formats had a single sample depth dependent definition
whereas the 8-bit formats had one page for each. Unify the documentation
of the 8-bit formats.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>