riscv: Add the T-HEAD SoC family Kconfig option

The first SoC in the T-HEAD series is TH1520, containing quad T-HEAD
C910 cores.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

arch/riscv/Kconfig.socs

@@ -41,6 +41,12 @@ config ARCH_SUNXI
 	  This enables support for Allwinner sun20i platform hardware,
 	  including boards based on the D1 and D1s SoCs.
 
+config ARCH_THEAD
+	bool "T-HEAD RISC-V SoCs"
+	select ERRATA_THEAD
+	help
+	  This enables support for the RISC-V based T-HEAD SoCs.
+
 config ARCH_VIRT
 	def_bool SOC_VIRT