can: sun4i_can: Only show Kconfig if ARCH_SUNXI is set

When adding the RISCV option I didn't gate it behind ARCH_SUNXI.
As a result this option shows up with Allwinner support isn't enabled.
Fix that by requiring ARCH_SUNXI to be set if RISCV is set.

Fixes: 8abb952 ("can: sun4i_can: Add support for the Allwinner D1")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/linux-sunxi/CAMuHMdV2m54UAH0X2dG7stEg=grFihrdsz4+o7=_DpBMhjTbkw@mail.gmail.com/
Signed-off-by: John Watts <contact@jookia.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/all/20230905231342.2042759-2-contact@jookia.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/Kconfig

@@ -190,7 +190,7 @@ config CAN_SLCAN
 
 config CAN_SUN4I
 	tristate "Allwinner A10 CAN controller"
-	depends on MACH_SUN4I || MACH_SUN7I || RISCV || COMPILE_TEST
+	depends on MACH_SUN4I || MACH_SUN7I || (RISCV && ARCH_SUNXI) || COMPILE_TEST
 	help
 	  Say Y here if you want to use CAN controller found on Allwinner
 	  A10/A20/D1 SoCs.