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>

arch/arm/boot/dts/vexpress-v2m-rs1.dtsi

@@ -66,7 +66,7 @@
 		};
 
 		iofpga@3,00000000 {
-			compatible = "arm,amba-bus", "simple-bus";
+			compatible = "simple-bus";
 			#address-cells = <1>;
 			#size-cells = <1>;
 			ranges = <0 3 0 0x200000>;