riscv: defconfig: enable T-HEAD SoC

Enable T-HEAD SoC config in defconfig to allow the default
upstream kernel to boot on Sipeed Lichee Pi 4A board.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

arch/riscv/configs/defconfig

@@ -27,6 +27,7 @@ CONFIG_EXPERT=y
 CONFIG_PROFILING=y
 CONFIG_SOC_MICROCHIP_POLARFIRE=y
 CONFIG_ARCH_RENESAS=y
+CONFIG_ARCH_THEAD=y
 CONFIG_SOC_SIFIVE=y
 CONFIG_SOC_STARFIVE=y
 CONFIG_ARCH_SUNXI=y