ipq40xx: add support for EnGenius EAP2200

ipq40xx: add support for EnGenius EAP2200

SOC:    IPQ4019 / QCA Dakota
CPU:    Quad-Core ARMv7 Processor rev 5 (v7l) Cortex-A7
DRAM:   256 MiB
FLASH:  NOR 4 MiB + NAND 128 MiB
ETH:    Qualcomm Atheros QCA8072
WLAN1:  Qualcomm Atheros QCA4019 2.4GHz 802.11bgn 2:2x2
WLAN2:  Qualcomm Atheros QCA4019 5GHz 802.11a/n/ac 2:2x2
WLAN2:  Qualcomm Atheros QCA9888 5GHz 802.11a/n/ac 2:2x2
INPUT:  WPS Button
LEDS:   Power, LAN1, LAN2, WLAN 2.4GHz, WLAN 5GHz-1, WLAN 5GHz-2, OPMODE

1. Load Ramdisk via U-Boot

To set up the flash memory environment, do the following:
a. As a preliminary step, ensure that the board console port is connected to the PC using these RS232 parameters:
   * 115200bps
   * 8N1
b. Confirm that the PC is connected to the board using one of the Ethernet ports.
c. Set a static ip 192.168.99.8 for Ethernet that connects to board.
d. The PC must have a TFTP server launched and listening on the interface to which the board is connected.
e. At this stage power up the board and, after a few seconds, press 4 and then any key during the countdown.

U-BOOT> set serverip 192.168.99.9 && tftpboot 0x84000000 192.168.99.8:openwrt.itb && bootm

Signed-off-by: Steven Lin <steven.lin@senao.com>
[copied 4.19 dts to 5.4]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>