board: gd32e103: fix kconfig CPU_HAS_ARM_MPU warning.

fix kconfig CPU_HAS_ARM_MPU warning.

Signed-off-by: YuLong Yao <[email protected]>

Author: feilongfl

boards/arm/gd32e103v_eval/gd32e103v_eval_defconfig

@@ -5,7 +5,7 @@ CONFIG_SOC_GD32E103VB=y
 CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=120000000
 
 # Enable MPU
-CONFIG_ARM_MPU=y
+# CONFIG_ARM_MPU=y
 
 # Enable HW stack protection
 # CONFIG_HW_STACK_PROTECTION=y