Exynos5260 SoCs have ARM GIC 400.  Correct the compatibles to match
dtschema and fix the dtbs_check warnings like:
  arch/arm/boot/dts/exynos5260-xyref5260.dt.yaml: interrupt-controller@
10481000:
    compatible: ['arm,cortex-a15-gic', 'arm,cortex-a9-gic'] is not valid under any of the given schemas
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200901075417.22481-3-krzk@kernel.org
                };
 
                gic: interrupt-controller@10481000 {
-                       compatible = "arm,cortex-a15-gic", "arm,cortex-a9-gic";
+                       compatible = "arm,gic-400", "arm,cortex-a15-gic";
                        #interrupt-cells = <3>;
                        #address-cells = <0>;
                        #size-cells = <0>;