boards: Holybro H7 boards clear MPU early in board init

- needed if the bootloader configures the memory protection unit (MPU)

boards/holybro/durandal-v1/src/init.c

@@ -75,6 +75,8 @@
 #include <px4_platform/board_determine_hw_info.h>
 #include <px4_platform/board_dma_alloc.h>
 
+#include <mpu.h>
+
 /****************************************************************************
  * Pre-Processor Definitions
  ****************************************************************************/
@@ -160,6 +162,16 @@ __EXPORT void board_on_reset(int status)
 __EXPORT void
 stm32_boardinitialize(void)
 {
+	// clear all existing MPU configuration from bootloader
+	for (int region = 0; region < CONFIG_ARM_MPU_NREGIONS; region++) {
+		putreg32(region, MPU_RNR);
+		putreg32(0, MPU_RBAR);
+		putreg32(0, MPU_RASR);
+
+		// save
+		putreg32(0, MPU_CTRL);
+	}
+
 	board_on_reset(-1); /* Reset PWM first thing */
 
 	/* configure LEDs */