plat: renesas: aarch64: Move to common

Move plat aarch64 code to common directory, so that the same
code can be re-used by both R-Car Gen3 and RZ/G2 platforms.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Change-Id: I66265e5e68bfcf5c3534965fb3549a145c782b47
4 files changed