ARM: dts: n900: remove unneeded unit name for dmtimer-pwm

This patch fixes the following DTC warnings for omap3-n900.dtb:

"dmtimer-pwm@9 has a unit name, but no reg property"
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap3-n900.dts

@@ -144,7 +144,7 @@ battery: n900-battery {
 		io-channel-names = "temp", "bsi", "vbat";
 	};
 
-	pwm9: dmtimer-pwm@9 {
+	pwm9: dmtimer-pwm {
 		compatible = "ti,omap-dmtimer-pwm";
 		#pwm-cells = <3>;
 		ti,timers = <&timer9>;