mips: mtmips: add two reference boards for mt7620

The mt7620_rfb board supports integrated 10/100M PHYs plus two external
giga PHYs. It also has 8MB SPI-NOR, mini PCI-e x1 slot, SDHC and USB.

The mt7620_mt7530_rfb boards supports an external MT7530 giga switch and a
16MB SPI-NOR flash.

Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/board/mediatek/mt7620/Kconfig b/board/mediatek/mt7620/Kconfig
new file mode 100644
index 0000000..b9137ad
--- /dev/null
+++ b/board/mediatek/mt7620/Kconfig
@@ -0,0 +1,12 @@
+if BOARD_MT7620_RFB || BOARD_MT7620_MT7530_RFB
+
+config SYS_BOARD
+	default "mt7620"
+
+config SYS_VENDOR
+	default "mediatek"
+
+config SYS_CONFIG_NAME
+	default "mt7620"
+
+endif