ARM: dts: am437x-gp-evm: Enable gpio.

Enable gpio3, gpio4, it will be used by gpio matrix keys. Also,
can be used by othe peripherals.
Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>

arch/arm/boot/dts/am437x-gp-evm.dts

@@ -69,3 +69,11 @@ &ecap0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&ecap0_pins>;
 };
+
+&gpio3 {
+	status = "okay";
+};
+
+&gpio4 {
+	status = "okay";
+};