ath79: DTS improvement for buzzer on RB951G-2HnD

Mikrotik RB951 router has a buzzer on the board, which makes annoying noises
due to the interference caused by PoE input or Wifi transmission
when no GPIO pin state is set.
I added buzzer node to device's DTS in order to set deault level to 1
and to provide easier access for it.

Signed-off-by: Pavel Pernička <pernicka.pa@gmail.com>
(cherry picked from commit dac0a133cf)

target/linux/ath79/dts/ar9344_mikrotik_routerboard-951g-2hnd.dts

@@ -17,6 +17,12 @@
 			gpio-export,output = <1>;
 			gpios = <&gpio 20 GPIO_ACTIVE_HIGH>;
 		};
+		
+		buzzer {
+			gpio-export,name = "buzzer";
+			gpio-export,output = <1>;
+			gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
+		};
 	};
 };