arm: rpi: Sync rpi dts files from Linux

Sync these files, obtained from Linux v5.15.

This adds a devicetree file for rpi_4 which was not there before.

Testing shows no change so far as I can see:
- boots to U-Boot prompt on rpi0, rpi2
- boots to distro on rpi3
- boots to distro on rpi4

I am assuming that syncing with Linux is safe, but the maintainer should
know for sure.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/bcm2835-rpi-cm1.dtsi b/arch/arm/dts/bcm2835-rpi-cm1.dtsi
index ef22c2d..e4e6b6a 100644
--- a/arch/arm/dts/bcm2835-rpi-cm1.dtsi
+++ b/arch/arm/dts/bcm2835-rpi-cm1.dtsi
@@ -5,11 +5,16 @@
 
 / {
 	leds {
-		act {
+		led-act {
 			gpios = <&gpio 47 GPIO_ACTIVE_LOW>;
 		};
 	};
 
+	memory@0 {
+		device_type = "memory";
+		reg = <0 0x20000000>;
+	};
+
 	reg_3v3: fixed-regulator {
 		compatible = "regulator-fixed";
 		regulator-name = "3V3";