RISC-V: introduce ARCH_FOO kconfig aliases for SOC_FOO symbols

To facilitate a transfer from SOC_FOO to ARCH_FOO, over a release cycle,
introduce some aliases so that drivers etc that use the SOC_FOO symbols
can be converted.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
To me, the most straight-forward conversion looks like so:
- this patch is applied in week 2 of the merge window, to avoid
  any conflicts with the Renesas tree
- all users of the SOC_ variants can be converted over a release cycle
  (or more) & no trees need to merge an immutable branch.
- we convert defconfig etc over after all users are converted
- doing it over at least one release cycle means that `make oldconfig`
  will keep people's configs working as they upgrade
- any new SoC families added uses ARCH_FOO

arch/riscv/Kconfig.socs

@@ -1,5 +1,8 @@
 menu "SoC selection"
 
+config ARCH_MICROCHIP_POLARFIRE
+	def_bool SOC_MICROCHIP_POLARFIRE
+
 config SOC_MICROCHIP_POLARFIRE
 	bool "Microchip PolarFire SoCs"
 	select MCHP_CLK_MPFS
@@ -11,6 +14,9 @@ config ARCH_RENESAS
 	help
 	  This enables support for the RISC-V based Renesas SoCs.
 
+config ARCH_SIFIVE
+	def_bool SOC_SIFIVE
+
 config SOC_SIFIVE
 	bool "SiFive SoCs"
 	select SERIAL_SIFIVE if TTY
@@ -21,6 +27,9 @@ config SOC_SIFIVE
 	help
 	  This enables support for SiFive SoC platform hardware.
 
+config ARCH_STARFIVE
+	def_bool SOC_STARFIVE
+
 config SOC_STARFIVE
 	bool "StarFive SoCs"
 	select PINCTRL
@@ -28,6 +37,9 @@ config SOC_STARFIVE
 	help
 	  This enables support for StarFive SoC platform hardware.
 
+config ARCH_VIRT
+	def_bool SOC_VIRT
+	
 config SOC_VIRT
 	bool "QEMU Virt Machine"
 	select CLINT_TIMER if RISCV_M_MODE
@@ -42,6 +54,9 @@ config SOC_VIRT
 	help
 	  This enables support for QEMU Virt Machine.
 
+config ARCH_CANAAN
+	def_bool SOC_CANAAN
+
 config SOC_CANAAN
 	bool "Canaan Kendryte K210 SoC"
 	depends on !MMU
@@ -57,6 +72,9 @@ config SOC_CANAAN
 
 if SOC_CANAAN
 
+config ARCH_CANAAN_K210_DTB_BUILTIN
+	def_bool SOC_CANAAN_K210_DTB_BUILTIN
+
 config SOC_CANAAN_K210_DTB_BUILTIN
 	bool "Builtin device tree for the Canaan Kendryte K210"
 	depends on SOC_CANAAN
@@ -68,6 +86,9 @@ config SOC_CANAAN_K210_DTB_BUILTIN
 	  This option should be selected if no bootloader is being used.
 	  If unsure, say Y.
 
+config ARCH_CANAAN_K210_DTB_SOURCE
+	def_bool SOC_CANAAN_K210_DTB_SOURCE
+
 config SOC_CANAAN_K210_DTB_SOURCE
 	string "Source file for the Canaan Kendryte K210 builtin DTB"
 	depends on SOC_CANAAN