powerpc/wii.dts: Add GPIO line names

These are the GPIO line names on a Nintendo Wii, as documented in:
https://wiibrew.org/wiki/Hardware/Hollywood_GPIOsSigned-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/dts/wii.dts

@@ -178,6 +178,14 @@ GPIO: gpio@d8000c0 {
 			gpio-controller;
 			ngpios = <24>;
 
+			gpio-line-names =
+				"POWER", "SHUTDOWN", "FAN", "DC_DC",
+				"DI_SPIN", "SLOT_LED", "EJECT_BTN", "SLOT_IN",
+				"SENSOR_BAR", "DO_EJECT", "EEP_CS", "EEP_CLK",
+				"EEP_MOSI", "EEP_MISO", "AVE_SCL", "AVE_SDA",
+				"DEBUG0", "DEBUG1", "DEBUG2", "DEBUG3",
+				"DEBUG4", "DEBUG5", "DEBUG6", "DEBUG7";
+
 			/*
 			 * This is commented out while a standard binding
 			 * for i2c over gpio is defined.