porting: Update ports syscfg

Author: Mynewt Bot

porting/npl/riot/include/syscfg/syscfg.h

@@ -321,6 +321,8 @@
 #define MYNEWT_VAL_SOFT_PWM (0)
 #endif
 
+#undef MYNEWT_VAL_ARM_MPU
+
 #ifndef MYNEWT_VAL_HAL_ENABLE_SOFTWARE_BREAKPOINTS
 #define MYNEWT_VAL_HAL_ENABLE_SOFTWARE_BREAKPOINTS (1)
 #endif