riscv: defconfig: enable SpacemiT SoC

Enable SpacemiT SoC config in defconfig to allow the default upstream
kernel booting on Banana Pi BPI-F3 board.

Signed-off-by: Yangyu Chen <cyy@cyyself.name>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Jesse Taube <jesse@rivosinc.com>
Signed-off-by: Yixun Lan <dlan@gentoo.org>

Author: cyyself

arch/riscv/configs/defconfig

@@ -30,6 +30,7 @@ CONFIG_ARCH_MICROCHIP=y
 CONFIG_ARCH_RENESAS=y
 CONFIG_ARCH_SIFIVE=y
 CONFIG_ARCH_SOPHGO=y
+CONFIG_ARCH_SPACEMIT=y
 CONFIG_SOC_STARFIVE=y
 CONFIG_ARCH_SUNXI=y
 CONFIG_ARCH_THEAD=y