doc: link whole-guide references to pages

Some references point to labels placed at the beginning of a file
only to link to the page as a whole.

Use :doc: links instead.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: David Marchand <david.marchand@redhat.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>