Docs: Fix broken URLs where possible.

The remaining broken links are to the tickets on the deprecated Phabricator.
Those URLs shall be updated after migrating the issues to TF-M GitHub mirror.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I3e8715bd4affc6829785f622804fa1f89116dd41
7 files changed