riscv: fu540: enable SMP

Signed-off-by: NLukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: NAnup Patel <anup.patel@wdc.com>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

board/sifive/fu540/Kconfig

@@ -38,5 +38,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	imply PHY_LIB
 	imply PHY_MSCC
 	imply SIFIVE_SERIAL
+	imply SMP
 
 endif