As per the trustedfirmware.org Project Maintenance Process [1], the
current maintainers of the TF-A project have nominated some contributors
to become maintainers themselves. List them in the maintainers.rst file
to make this official.

[1] https://developer.trustedfirmware.org/w/collaboration/project-maintenance-process/

Change-Id: Id4e3cfd12a9074f4e255087fa5dd6fa5f902845f
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>