ARM: dts: am437x-gp-evm: Add vtt_fixed regulator

The VTT regulator for DDR3 termination on the am437x-gp-evm is
controlled by a gpio. It is configured by the bootloader so here we
define an always-on, fixed voltage regulator to hold the gpio.
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

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

@@ -27,6 +27,17 @@ vmmcsd_fixed: fixedregulator-sd {
 		enable-active-high;
 	};
 
+	vtt_fixed: fixedregulator-vtt {
+		compatible = "regulator-fixed";
+		regulator-name = "vtt_fixed";
+		regulator-min-microvolt = <1500000>;
+		regulator-max-microvolt = <1500000>;
+		regulator-always-on;
+		regulator-boot-on;
+		enable-active-high;
+		gpio = <&gpio5 7 GPIO_ACTIVE_HIGH>;
+	};
+
 	backlight {
 		compatible = "pwm-backlight";
 		pwms = <&ecap0 0 50000 PWM_POLARITY_INVERTED>;