ipq40xx: add support for GL.iNet GL-AP1300

ipq40xx: add support for GL.iNet GL-AP1300

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 5GHz 802.11n/ac W2 2x2
INPUT:      Reset
LED:        Power, Internet
UART1:      On board pin header near to LED (3.3V, TX, RX, GND), 3.3V without pin - 115200 8N1
OTHER:      On board with BLE module - by cp210x USB serial chip
            On board hareware watchdog with GPIO0 high to turn on, and GPIO4 for watchdog feed

Install via uboot tftp or uboot web failsafe.

By uboot tftp:
(IPQ40xx) # tftpboot 0x84000000 openwrt-ipq40xx-generic-glinet_gl-ap1300-squashfs-nand-factory.ubi
(IPQ40xx) # run lf

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: Dongming Han <handongming@gl-inet.com>