arm64: dts: fvp: Fix GIC compatible names

The GIC DT binding only allows certain combinations of DT compatible
strings. The somewhat awkward "arm,cortex-a15-gic", "arm,cortex-a9-gic"
is not among those.

Drop that combination of different "cortex" based strings used for the
models, and replace it with the more useful combination including
"arm,gic-400".

Link: https://lore.kernel.org/r/20200513103016.130417-9-andre.przywara@arm.comSigned-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

arch/arm64/boot/dts/arm/foundation-v8-gicv2.dtsi

@@ -6,7 +6,7 @@
 
 / {
 	gic: interrupt-controller@2c001000 {
-		compatible = "arm,cortex-a15-gic", "arm,cortex-a9-gic";
+		compatible = "arm,gic-400", "arm,cortex-a15-gic";
 		#interrupt-cells = <3>;
 		#address-cells = <2>;
 		interrupt-controller;

arch/arm64/boot/dts/arm/rtsm_ve-aemv8a.dts

@@ -95,7 +95,7 @@ vram: vram@18000000 {
 	};
 
 	gic: interrupt-controller@2c001000 {
-		compatible = "arm,cortex-a15-gic", "arm,cortex-a9-gic";
+		compatible = "arm,gic-400", "arm,cortex-a15-gic";
 		#interrupt-cells = <3>;
 		#address-cells = <0>;
 		interrupt-controller;