ipq40xx: add support for GL.iNet GL-A1300

ipq40xx: add support for GL.iNet GL-A1300

Specifications:
SOC:		Qualcomm IPQ4018 (DAKOTA) ARM Quad-Core
RAM:		256 MiB
FLASH1:		4 MiB NOR
FLASH2:		128 MiB NAND
ETH:		Qualcomm QCA8075
WLAN1:		Qualcomm Atheros QCA4018 2.4GHz 802.11b/g/n 2x2
WLAN2:		Qualcomm Atheros QCA4018 5G 802.11n/ac W2 2x2
USB:		1 x USB 3.0 port
Button:		1 x Reset button
Switch:		1 x Mode switch
LED:		1 x Blue LED + 1 x White LED

Install via uboot tftp or uboot web failsafe.

By uboot tftp:
(IPQ40xx) # tftpboot 0x84000000 openwrt-ipq40xx-generic-glinet_gl-a1300-squashfs-nand-factory.ubi
(IPQ40xx) # nand erase 0 0x8000000
(IPQ40xx) # nand write 0x84000000 0 $filesize

By uboot web failsafe:
Push the reset button for 10 seconds util the power led flash faster,
then use broswer to access http://192.168.1.1

Afterwards upgrade can use sysupgrade image.

Signed-off-by: Weiping Yang <weiping.yang@gl-inet.com>