ARM: gr8: Add the UART3

The GR8 has access to the UART3 controller, which was missing in the
DTSI. Add it.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>

arch/arm/boot/dts/sun5i-gr8.dtsi

@@ -978,6 +978,16 @@ uart2: serial@01c28800 {
 			status = "disabled";
 		};
 
+		uart3: serial@01c28c00 {
+			compatible = "snps,dw-apb-uart";
+			reg = <0x01c28c00 0x400>;
+			interrupts = <4>;
+			reg-shift = <2>;
+			reg-io-width = <4>;
+			clocks = <&apb1_gates 19>;
+			status = "disabled";
+		};
+
 		i2c0: i2c@01c2ac00 {
 			compatible = "allwinner,sun4i-a10-i2c";
 			reg = <0x01c2ac00 0x400>;