riscv: Kconfig.socs: Add ARCH_RENESAS kconfig option

Add ARCH_RENESAS config option to allow selecting the Renesas RISC-V SoCs.
We currently have the newly added RZ/Five (R9A07G043) RISC-V based SoC.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20221028165921.94487-4-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/riscv/Kconfig.socs

@@ -7,6 +7,11 @@ config SOC_MICROCHIP_POLARFIRE
 	help
 	  This enables support for Microchip PolarFire SoC platforms.
 
+config ARCH_RENESAS
+	bool "Renesas RISC-V SoCs"
+	help
+	  This enables support for the RISC-V based Renesas SoCs.
+
 config SOC_SIFIVE
 	bool "SiFive SoCs"
 	select SERIAL_SIFIVE if TTY