[media] DocBook: some fixes at FE_GET_INFO

There are a few issues at FE_GET_INFO documentation:
- name is a string, not a pointer to a string;
- the return text should be after the paragraph.

While here, better to bold that two fields of the structure used
by FE_GET_INFO are actually deprecated.

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