rcar_gen3: plat: Add R-Car V3M support

Add R-Car V3M support. This is based on the original
V3M support patch for Yocto v2.23.1 by Vladimir Barinov.

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
---
Marek: Update on top of mainline ATF/master
22 files changed