Add support for MT7622 reference board

This adds a general board file based on MT7622 SoCs from MediaTek.
This commit is adding the basic boot support for the MT7622 rfb.

Tested-by: Frank Wunderlich <frank-w@public-files.de>
diff --git a/board/mediatek/mt7622/Kconfig b/board/mediatek/mt7622/Kconfig
new file mode 100644
index 0000000..d0abdc0
--- /dev/null
+++ b/board/mediatek/mt7622/Kconfig
@@ -0,0 +1,17 @@
+if TARGET_MT7622
+
+config SYS_BOARD
+	default "mt7622"
+
+config SYS_CONFIG_NAME
+	default "mt7622"
+
+config MTK_BROM_HEADER_INFO
+	string
+	default "lk=1"
+
+config MTK_BROM_HEADER_INFO
+	string
+	default "media=nor"
+
+endif