ARM: shmobile: porter: add I2C2 DT support

Define the Porter board dependent part of the I2C2 device node.

This patch is  analogous to the commit 29a647c3 ("ARM: shmobile:
henninger: add I2C2 DT support") as there are no differences between
the boards in this respect.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791-porter.dts

@@ -109,6 +109,11 @@ sdhi2_pins: sd2 {
 		renesas,groups = "sdhi2_data4", "sdhi2_ctrl";
 		renesas,function = "sdhi2";
 	};
+
+	i2c2_pins: i2c2 {
+		renesas,groups = "i2c2";
+		renesas,function = "i2c2";
+	};
 };
 
 &scif0 {
@@ -155,6 +160,14 @@ &sdhi2 {
 	status = "okay";
 };
 
+&i2c2 {
+	pinctrl-0 = <&i2c2_pins>;
+	pinctrl-names = "default";
+
+	status = "okay";
+	clock-frequency = <400000>;
+};
+
 &sata0 {
 	status = "okay";
 };