platform: generic: Add Renesas RZ/Five initial support

platform: generic: Add Renesas RZ/Five initial support

This commit provides basic support for the Renesas RZ/Five
(R9A07G043F) SoC.

The RZ/Five microprocessor includes a single RISC-V CPU Core (Andes AX45MP)
1.0 GHz, 16-bit DDR3L/DDR4 interface. Supported interfaces include:
- Gigabit Ethernet 2ch
- CAN interface (CAN-FD) 2ch
- USB 2.0 interface 2ch
- SD interface 2ch
- AD converter 2ch

Useful links:
-------------
Links: https://www.renesas.com/us/en/products/microcontrollers-microprocessors/rz-mpus/rzfive-risc-v-general-purpose-microprocessors-risc-v-cpu-core-andes-ax45mp-single-10-ghz-2ch-gigabit-ethernet
Links: http://www.andestech.com/en/products-solutions/andescore-processors/riscv-ax45mp/

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Anup Patel <anup@brainfault.org>