Update arduino_portenta_h7_m7.overlay

Add dma sections to remove the build warnings

Author: KurtE

loader/boards/arduino_portenta_h7_m7.overlay

@@ -40,6 +40,14 @@
 	pinctrl-names = "default";
 };
 
+&dmamux1 {
+	status = "okay";
+};
+
+&dma1 {
+	status = "okay";
+};
+
 &rng {
 	status = "okay";
 };