ARM: BCM5301X: Drop unused poll-interval from gpio-keys

It was accidentally left (& copied & pasted all around) from our
experiments with gpio-keys-polled.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

arch/arm/boot/dts/bcm4708-buffalo-wzr-1750dhp.dts

@@ -27,7 +27,6 @@ gpio-keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;
-		poll-interval = <200>;
 
 		restart {
 			label = "Reset";

arch/arm/boot/dts/bcm4708-netgear-r6250.dts

@@ -71,7 +71,6 @@ gpio-keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;
-		poll-interval = <200>;
 
 		wps {
 			label = "WPS";

arch/arm/boot/dts/bcm4708-netgear-r6300-v2.dts

@@ -61,7 +61,6 @@ gpio-keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;
-		poll-interval = <200>;
 
 		wps {
 			label = "WPS";

arch/arm/boot/dts/bcm47081-asus-rt-n18u.dts

@@ -61,7 +61,6 @@ gpio-keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;
-		poll-interval = <200>;
 
 		restart {
 			label = "Reset";

arch/arm/boot/dts/bcm47081-buffalo-wzr-600dhp2.dts

@@ -27,7 +27,6 @@ gpio-keys {
 		compatible = "gpio-keys";
 		#address-cells = <1>;
 		#size-cells = <0>;
-		poll-interval = <200>;
 
 		aoss {
 			label = "AOSS";