ARM: dts: aspeed-g5: Add SCU phandle to GFX node

In v5.13 the DRM driver gained support for using a phandle to the SCU,
instead of matching on the scu compatible.

Link: https://lore.kernel.org/r/20210603064536.165297-1-joel@jms.id.auSigned-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-g5.dtsi

@@ -264,6 +264,7 @@ gfx: display@1e6e6000 {
 				reg-io-width = <4>;
 				clocks = <&syscon ASPEED_CLK_GATE_D1CLK>;
 				resets = <&syscon ASPEED_RESET_CRT1>;
+				syscon = <&syscon>;
 				status = "disabled";
 				interrupts = <0x19>;
 			};