ipq40xx: add support for ASUS Lyra

ipq40xx: add support for ASUS Lyra

SoC:   Qualcomm IPQ4019 (Dakota) 717 MHz, 4 cores
RAM:   256 MiB (Nanya NT5CC128M16IP-DI)
FLASH: 128 MiB (Macronix NAND)
WiFi0: Qualcomm IPQ4019 b/g/n 2x2
WiFi1: Qualcomm IPQ4019 a/n/ac 2x2
WiFi2: Qualcomm Atheros QCA9886 a/n/ac
BT:    Atheros AR3012
IN:    WPS Button, Reset Button
OUT:   RGB-LED via TI LP5523 9-channel Controller
UART:  Front of Device - 115200 N-8
       Pinout 3.3v - RX - TX - GND (Square is VCC)

Installation:
1. Transfer OpenWRT-initramfs image to the device via SSH to /tmp.
Login credentials are identical to the Web UI.

2. Login to the device via SSH.

3. Flash the initramfs image using

> mtd-write -d linux -i openwrt-image-file

4. Power-cycle the device and wait for OpenWRT to boot.

5. From there flash the OpenWRT-sysupgrade image.

Ethernet-Ports: Although labeled identically, the port next to
the power socket is the LAN port and the other one is WAN. This
is the same behavior as in the stock firmware.

Signed-off-by: Marius Genheimer <mail@f0wl.cc>
[Dropped setup_mac 02_network in favour of 05_set_iface_mac_ipq40xx.sh,
reorderd 02_network entries, added board.bin WA for the QCA9886 from ath79,
minor dts touchup, added rng to 4.19 dts]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>