ARM, ARM64: dts: drop "arm,amba-bus" in favor of "simple-bus"

The compatible string "simple-bus" is well defined in ePAPR, while
I see no documentation for the "arm,amba-bus" arnywhere in ePAPR or
Documentation/devicetree/.

DT is also used by other projects than Linux kernel.  It is not a
good idea to rely on such an unofficial binding.

This commit
  - replaces "arm,amba-bus" with "simple-bus"
  - drops "arm,amba-bus" where it is used along with "simple-bus"

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
diff --git a/arch/arm/boot/dts/rk3036.dtsi b/arch/arm/boot/dts/rk3036.dtsi
index 3864fa1..597fdc4 100644
--- a/arch/arm/boot/dts/rk3036.dtsi
+++ b/arch/arm/boot/dts/rk3036.dtsi
@@ -95,7 +95,7 @@
 	};
 
 	amba {
-		compatible = "arm,amba-bus";
+		compatible = "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;
 		ranges;