dt-bindings: memory: renesas,rpc-if: Add support for RZ/G2 Series

The RZ/G2 Series has the RPC-IF interface.  Update bindings to support:
r8a774a1, r8a774b1, r8a774c0, and r8a774e1

Signed-off-by: Adam Ford <aford173@gmail.com>
Link: https://lore.kernel.org/r/20210102115412.3402059-1-aford173@gmail.com


Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>