[media] DocBook: move data types to a separate section

As MEDIA_IOC_G_TOPOLOGY shares the data types already declared
for entities, pads and links, we should move those to a separate
part of the document, and use cross-references where needed.

So, move the following tables to a separate section at the
DocBook:
	media-entity-type
	media-entity-flag
	media-pad-flag
	media-link-flag

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>