arm64: dts: exynos: add proper comaptible FSYS syscon in Exynos5433

The syscon nodes should come with specific compatible.  Correct the
FSYS syscon to fix dtbs_check warnings:

  syscon@156f0000: compatible: 'anyOf' conditional failed, one must be fixed:
  ['syscon'] is too short
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20210820082149.84613-1-krzysztof.kozlowski@canonical.com

arch/arm64/boot/dts/exynos/exynos5433.dtsi

@@ -1132,7 +1132,7 @@ syscon_cam1: syscon@145f0000 {
 		};
 
 		syscon_fsys: syscon@156f0000 {
-			compatible = "syscon";
+			compatible = "samsung,exynos5433-sysreg", "syscon";
 			reg = <0x156f0000 0x1044>;
 		};