ramips: fix to mt7620a and add support for i2c on WD03

There was an error on initial commit, the proper soc is mt7620n (which is
more limited than mt7620a). Moreover, there is a battery management
controller connected to the i2c port of the mt7620n. I have a small piece
of i2c code to get battery level coming.

Signed-off-by: Matthias Badaire <mbadaire@gmail.com>

target/linux/ramips/dts/WD03.dts

@@ -6,7 +6,7 @@
 #include <dt-bindings/input/input.h>
 
 / {
-	compatible = "ravpower,wd03", "ralink,mt7620a-soc";
+	compatible = "ravpower,wd03", "ralink,mt7620n-soc";
 	model = "Ravpower WD03";
 
 	chosen {
@@ -50,6 +50,10 @@
 	status = "okay";
 };
 
+&i2c {
+        status = "okay";
+};
+
 &spi0 {
 	status = "okay";