Update armv8m_mpu.h - adding void

Removes error:
error: old-style function definition [-Werror=old-style-definition]

CMSIS/Core/Include/m-profile/armv8m_mpu.h

@@ -188,7 +188,7 @@ typedef struct {
   \brief  Read MPU Type Register
   \return Number of MPU regions
 */
-__STATIC_INLINE uint32_t ARM_MPU_TYPE()
+__STATIC_INLINE uint32_t ARM_MPU_TYPE(void)
 {
   return ((MPU->TYPE) >> 8);
 }