Portenta: set 3V1 rail to provide 1.5A

The ripple on that rail with low power consumption was creating issues with Bluetooth module initialization

Author: facchinm

variants/PORTENTA_H7_M7/variant.cpp

@@ -53,11 +53,22 @@ extern "C" {
   }
 }
 
+#include "drivers/I2C.h"
+
+void fixup3V1Rail() {
+  mbed::I2C i2c(PB_7, PB_6);
+  char data[2];
+  data[0]=0x42;
+  data[1]=(1);
+  i2c.write(8 << 1, data, sizeof(data));
+}
+
 void initVariant() {
   RTCHandle.Instance = RTC;
   // Turn off LED from bootloader
   pinMode(PK_6, OUTPUT);
   digitalWrite(PK_6, HIGH);
+  fixup3V1Rail();
 }
 
 #ifdef SERIAL_CDC