Update repository URL in the documentation

TF-A and TF-A Tests git repositories are getting moved to a TF-A/
namespace in order to easily identify what repos are for TF-A or TF-M.

Change-Id: Id3e9ae299fa4e0dd8699c967879cd8ce5a17c940
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
3 files changed