feat(rme): add ENABLE_RME build option and support for RMM image

The changes include:

- A new build option (ENABLE_RME) to enable FEAT_RME

- New image called RMM. RMM is R-EL2 firmware that manages Realms.
  When building TF-A, a path to RMM image can be specified using
  the "RMM" build flag. If RMM image is not provided, TRP is built
  by default and used as RMM image.

- Support for RMM image in fiptool

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: I017c23ef02e465a5198baafd665a60858ecd1b25
10 files changed