ipq40xx: add support for GL.iNet GL-S1300

ipq40xx: add support for GL.iNet GL-S1300

Specifications:
SOC:        Qualcomm IPQ4029 (DAKOTA) ARM Quad-Core
RAM:        512 MiB
FLASH1:     16 MiB NOR - SPI0
FLASH2:     8 GiB eMMC
ETH:        Qualcomm QCA8075
WLAN1:      Qualcomm Atheros QCA4029 2.4GHz 802.11b/g/n 2x2
WLAN2:      Qualcomm Atheros QCA4029 5GHz 802.11n/ac W2 2x2
INPUT:      Reset, WPS
LED:        Power, Mesh, WLAN
UART1:      On board pin header near to LED (3.3V, TX, RX, GND), 3.3V without pin - 115200 8N1
UART2:      On board with BLE module
SPI1:       On board socket for Zigbee module

Install via tftp
- NB: need to flash transition image firstly

Firstly install transition image:
(IPQ40xx) # tftpboot 0x84000000 s1300-factory-to-openwrt.img
(IPQ40xx) # sf probe && imgaddr=0x84000000 && source :script

Secondly install openwrt sysupgrade bin:
(IPQ40xx) # run lf

Revert to factory image:
(IPQ40xx) # tftpboot 0x84000000 s1300-openwrt-to-factory.img
(IPQ40xx) # sf probe && imgaddr=0x84000000 && source :script

The kernel and rootfs of factory firmware are on eMMC, and openwrt
firmware is on NOR flash. The transition image includes U-boot
and partition table, which decides where to load kernel and rootfs.
After you firstly install openwrt image, you can switch between
factory and openwrt firmware by flashing transition image.

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