sunxi: A64: Re-add syscon to DT node

The sun50i-a64.dtsi changes introduced in Linux v4.19-rc1 changed the
compatible name for the syscon controller, dropping the generic "syscon"
fallback. Using this new DT node will make the Ethernet driver in every
older kernel (or non-Linux kernels) fail to initialise the MAC device.

To allow booting distribution kernels (from installer images via UEFI,
for instance), re-add the syscon compatible string as a fallback. This
works with both older and newer kernels.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
diff --git a/arch/arm/dts/sun50i-a64.dtsi b/arch/arm/dts/sun50i-a64.dtsi
index f3a66f8..ff41abc 100644
--- a/arch/arm/dts/sun50i-a64.dtsi
+++ b/arch/arm/dts/sun50i-a64.dtsi
@@ -259,7 +259,8 @@
 		};
 
 		syscon: syscon@1c00000 {
-			compatible = "allwinner,sun50i-a64-system-control";
+			compatible = "allwinner,sun50i-a64-system-control",
+				"syscon";
 			reg = <0x01c00000 0x1000>;
 			#address-cells = <1>;
 			#size-cells = <1>;