net: add ethernet driver for MediaTek MT7620 SoC

This patch adds  ethernet driver for MediaTek MT7620 SoC.

The MT7620 SoC has a built-in ethernet (Frame Engine) and a built-in
7-port switch and two xMII interfaces (can be MII/RMII/RGMII).

The port 0-3 of the switch connects to intergrited FE PHYs. Port 4 can be
configured to connect to either the intergrited FE PHY, or the xMII.
Port 5 always connects to the xMII. Port 6 is the CPU port.

This driver supports MT7530 giga switch connects to port 5.

Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index e3bdda3..f2a0df5 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -44,6 +44,7 @@
 obj-$(CONFIG_MDIO_MUX_I2CREG) += mdio_mux_i2creg.o
 obj-$(CONFIG_MDIO_MUX_SANDBOX) += mdio_mux_sandbox.o
 obj-$(CONFIG_MPC8XX_FEC) += mpc8xx_fec.o
+obj-$(CONFIG_MT7620_ETH) += mt7620-eth.o
 obj-$(CONFIG_MT7628_ETH) += mt7628-eth.o
 obj-$(CONFIG_MVGBE) += mvgbe.o
 obj-$(CONFIG_MVMDIO) += mvmdio.o