uboot-envtools: Add u-boot env config for GL-MT3000

This commit add u-boot env config for GL-MT3000, so
that we can use fw_printenv to print u-boot env and
use fw_setenv to set u-boot env in GL-MT3000.

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>
(cherry picked from commit 6892603efa)

package/boot/uboot-envtools/files/mediatek_filogic

@@ -37,6 +37,9 @@ bananapi,bpi-r3)
 		;;
 	esac
 	;;
+glinet,gl-mt3000)
+	ubootenv_add_uci_config "/dev/mtd1" "0x0" "0x80000" "0x20000"
+	;;
 netgear,wax220)
 	ubootenv_add_uci_config "/dev/mtd5" "0x0" "0x20000" "0x20000"
 	;;