riscv: ae350: enable SMP

Signed-off-by: Rick Chen <rick@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
diff --git a/board/AndesTech/ax25-ae350/Kconfig b/board/AndesTech/ax25-ae350/Kconfig
index 44cb302..5e682b6 100644
--- a/board/AndesTech/ax25-ae350/Kconfig
+++ b/board/AndesTech/ax25-ae350/Kconfig
@@ -24,5 +24,6 @@
 config BOARD_SPECIFIC_OPTIONS # dummy
 	def_bool y
 	select RISCV_NDS
+	imply SMP
 
 endif