ramips: Add support for GL-MT750

This patch adds support for GL-MT750.
GL-MT750 is powered by MT7620A and MT7610e, dual band 802.11ac, 2.4G 300Mbps and 5G 450Mbps.
It has 5 LANs, MMC interface, USB, a lot of IOs and PoE support.

SVN-Revision: 48994

target/linux/ramips/base-files/lib/ramips.sh

@@ -181,6 +181,9 @@ ramips_board_detect() {
 	*"GL-MT300N")
 		name="gl-mt300n"
 		;;
+	*"GL-MT750")
+		name="gl-mt750"
+		;;
 	*"HC5661")
 		name="hc5661"
 		;;