ARM: tegra: Add missing HDMI +5V regulator

Commit fb50a116 ("drm/tegra: hdmi - Add connector supply support")
introduced a new supply for HDMI connectors that is used to control the
voltage on the +5V pin. Not all boards have had the corresponding supply
added to their device tree files, causing the following warning message
during boot:

	[    0.859698] 54280000.hdmi supply hdmi not found, using dummy regulator

Add such a regulator to the Seaboard DTS to enable the driver to control
this voltage and get rid of the warning.
Reported-by: NStephen Warren <swarren@nvidia.com>
Tested-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-seaboard.dts

@@ -31,6 +31,7 @@
 
 			vdd-supply = <&hdmi_vdd_reg>;
 			pll-supply = <&hdmi_pll_reg>;
+			hdmi-supply = <&vdd_hdmi>;
 
 			nvidia,ddc-i2c-bus = <&hdmi_ddc>;
 			nvidia,hpd-gpio = <&gpio TEGRA_GPIO(N, 7)
@@ -893,6 +894,17 @@
 			gpio = <&gpio TEGRA_GPIO(W, 0) GPIO_ACTIVE_HIGH>;
 			enable-active-high;
 		};
+
+		vdd_hdmi: regulator@6 {
+			compatible = "regulator-fixed";
+			reg = <6>;
+			regulator-name = "VDDIO_HDMI";
+			regulator-min-microvolt = <5000000>;
+			regulator-max-microvolt = <5000000>;
+			gpio = <&gpio TEGRA_GPIO(V, 5) GPIO_ACTIVE_HIGH>;
+			enable-active-high;
+			vin-supply = <&vdd_5v0_reg>;
+		};
 	};
 
 	sound {