docs(maintainers): add PSA, MHU, RSS comms code owners

Adding Sandrine Bailleux for the PSA APIs and myself for the
MHU and RSS comms drivers as code owner.

Change-Id: Ib948479cc6e46163aae59c938877a2d0bcf91754
Signed-off-by: David Vincze <david.vincze@arm.com>
1 file changed