airoha: an7581: add airoha,chip-scu phandle to scuclk node

The clk-en7523 driver tries to look up the chip-scu regmap via the
"airoha,chip-scu" phandle first. If absent, it falls back to a
compatible-based lookup with syscon_regmap_lookup_by_compatible().

The AN7583 DTSI already had the phandle but AN7581 did not, relying
on the fallback instead. Add it so the DT explicitly describes the
connection and both platforms use the same lookup path.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

target/linux/airoha/dts/an7581.dtsi

@@ -578,6 +578,8 @@
 			reg = <0x0 0x1fb00000 0x0 0x970>;
 			#clock-cells = <1>;
 			#reset-cells = <1>;
+
+			airoha,chip-scu = <&chip_scu>;
 		};
 
 		rng@1faa1000 {