ARM64: dts: meson-gxl: add the pwm_ao_b pin

This adds the pwm_ao_b pin to allow boards which have an LED connected
to GPIOAO_9 to use the leds-pwm driver (by activating the pwm_AO_ab node
and passing the pwm_ao_b_pin pinctrl-reference).
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxl.dtsi

@@ -117,6 +117,13 @@ mux {
 				function = "remote_input_ao";
 			};
 		};
+
+		pwm_ao_b_pins: pwm_ao_b {
+			mux {
+				groups = "pwm_ao_b";
+				function = "pwm_ao_b";
+			};
+		};
 	};
 };