mt7622: bpi-r64: enable using mt7531 switch irq

Now that we support link-state-change interrupts, wire up MT7531 IRQ
line which is connected to GPIO#53 according to the schematics [1].

As a result, PHY state no longer needs to be polled on that board.

[1]: https://forum.banana-pi.org/t/bpi-r64-mt7622-schematic-diagram-public/10118
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/mediatek/patches-5.10/180-dts-mt7622-bpi-r64-add-mt7531-irq.patch

@@ -0,0 +1,13 @@
+--- a/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts
++++ b/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts
+@@ -160,6 +160,10 @@
+ 		switch@0 {
+ 			compatible = "mediatek,mt7531";
+ 			reg = <0>;
++			interrupt-controller;
++			#interrupt-cells = <1>;
++			interrupt-parent = <&pio>;
++			interrupts = <53 IRQ_TYPE_LEVEL_HIGH>;
+ 			reset-gpios = <&pio 54 0>;
+ 
+ 			ports {