memory: renesas-rpc-if: Add support for RZ/G2L

SPI Multi I/O Bus Controller on RZ/G2L SoC is almost identical to
the RPC-IF interface found on R-Car Gen3 SoC's.

This patch adds a new compatible string for the RZ/G2L family so
that the timing values on RZ/G2L can be adjusted.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20211025205631.21151-8-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>