fix MPU compilation issue

Author: caixue1102

targets/TARGET_RDA/TARGET_UNO_91H/device/RDA5991H.h

@@ -70,7 +70,7 @@ typedef enum IRQn
  */
 
 /* Configuration of the Cortex-M4 Processor and Core Peripherals */
-#define __MPU_PRESENT             1         /*!< MPU present or not                               */
+#define __MPU_PRESENT             0         /*!< MPU present or not                               */
 #define __NVIC_PRIO_BITS          5         /*!< Number of Bits used for Priority Levels          */
 #define __Vendor_SysTickConfig    0         /*!< Set to 1 if different SysTick Config is used     */
 #define __FPU_PRESENT             1         /*!< FPU present                                      */

targets/targets.json

@@ -7921,7 +7921,21 @@
         "extra_labels": ["RDA", "UNO_91H", "FLASH_CMSIS_ALGO"],
         "supported_toolchains": ["ARM", "GCC_ARM", "IAR"],
         "macros": ["TWO_RAM_REGIONS", "CMSIS_NVIC_VIRTUAL", "CMSIS_NVIC_VIRTUAL_HEADER_FILE=\"RDA5981_nvic_virtual.h\""],
-        "device_has": ["USTICKER", "PORTIN", "PORTOUT", "PORTINOUT", "INTERRUPTIN", "SERIAL", "STDIO_MESSAGES", "PWMOUT", "SPI", "SLEEP", "ANALOGIN", "FLASH", "TRNG", "MPU"],
+        "device_has": [
+            "USTICKER",
+            "PORTIN",
+            "PORTOUT",
+            "PORTINOUT",
+            "INTERRUPTIN",
+            "SERIAL",
+            "STDIO_MESSAGES",
+            "PWMOUT",
+            "SPI",
+            "SLEEP",
+            "ANALOGIN",
+            "FLASH",
+            "TRNG"
+        ],
         "release_versions": ["2", "5"]
     },
     "UNO_91H": {