ARM: dts: rmobile: Reinstate missing i2c6 on Porter

The I2C6 is used to communicate with the PMIC and it was removed
during DT sync with Linux 4.17. Reinstate it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>

arch/arm/dts/r8a7791-porter.dts

@@ -372,6 +372,11 @@
 	clock-frequency = <400000>;
 };
 
+&i2c6 {
+	status = "okay";
+	clock-frequency = <400000>;
+};
+
 &sata0 {
 	status = "okay";
 };