ARM: dts: bcm2835: Change firmware compatible from simple-bus to simple-mfd

The current binding for the RPi firmware uses the simple-bus compatible as
a fallback to benefit from its automatic probing of child nodes.

However, simple-bus also comes with some constraints, like having the ranges,
our case.

Let's switch to simple-mfd that provides the same probing logic without
those constraints.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20200924082642.18144-1-maxime@cerno.tech
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml

@@ -23,7 +23,7 @@ properties:
   compatible:
     items:
       - const: raspberrypi,bcm2835-firmware
-      - const: simple-bus
+      - const: simple-mfd
 
   mboxes:
     $ref: '/schemas/types.yaml#/definitions/phandle'
@@ -57,7 +57,7 @@ required:
 examples:
   - |
     firmware {
-        compatible = "raspberrypi,bcm2835-firmware", "simple-bus";
+        compatible = "raspberrypi,bcm2835-firmware", "simple-mfd";
         mboxes = <&mailbox>;
 
         firmware_clocks: clocks {

arch/arm/boot/dts/bcm2835-rpi.dtsi

@@ -13,7 +13,7 @@ act {
 
 	soc {
 		firmware: firmware {
-			compatible = "raspberrypi,bcm2835-firmware", "simple-bus";
+			compatible = "raspberrypi,bcm2835-firmware", "simple-mfd";
 			#address-cells = <1>;
 			#size-cells = <1>;