arm64: dts: Add ethernet Aliases to BananaPi R4

U-boot uses the ethernet aliases in the device-tree that is used by
Linux to determine which nodes to modify to pass mac-address details
configured in u-boot into Linux.

This fixup is performed in u-boot in fdt_fixup_ethernet()

Signed-off-by: Sachi King <nakato@nakato.io>

arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dts

@@ -23,6 +23,9 @@
 		led-failsafe = &led_green;
 		led-running = &led_green;
 		led-upgrade = &led_green;
+		ethernet0 = &gmac0;
+		ethernet1 = &gmac1;
+		ethernet2 = &gmac2;
 	};
 
 	chosen {