fix(docs): replace deprecated urls under tfa/docs

Fixed internal links refrenced inside tfa/docs.
Followed https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#ref-role
for instrustion on how to link sections within other documents.

Signed-off-by: Thaddeus Serna <thaddeus.gonzalez-serna@arm.com>
Change-Id: I8e7c090d98951b1e3d393ab5b1d6bcdaa1865c6f
6 files changed