ath79: add support for Netgear PGZNG1

ath79: add support for Netgear PGZNG1

This adds support for the Netgear PGZNG1, also known as the ADT Pulse
Gateway.

Hardware:
CPU: Atheros AR9344
Memory: 256MB
Storage: 256MB NAND Hynix H27U2G8F2CTR-BC
USB: 1x USB 2.0
Ethernet: 2x 100Mb/s
WiFi: Atheros AR9340 2.4GHz 2T2R
Leds: 8 LEDs
Button: 1x Reset Button
UART:
Header marked JPE1. Pinout is VCC, TX, RX, GND. The marked pin, closest
to the JPE1 marking, is VCC. Note VCC isn't required to be connected
for UART to work.

Enable Stock Firmware Shell Access:
1. Interrupt u-boot and run the following commands
setenv console_mode 1
saveenv
reset

This will enable a UART shell in the firmware. You can then login using
the root password of `icontrol`. If that doesn't work, the device is
running a firmware based on OpenWRT where you can drop into failsafe to
mount the FS and then modify /etc/passwd.

Installation Instructions:
1. Interupt u-boot and run the following commands
setenv active_image 0
setenv stock_bootcmd nboot 0x81000000 0 \${kernel_offset}
setenv openwrt_bootcmd nboot 0x82000000 0 \${kernel_offset}
setenv bootcmd run openwrt_bootcmd
saveenv

2. boot initramfs image via TFTP u-boot
tftpboot 0x82000000 openwrt-ath79-nand-netgear_pgzng1-initramfs-kernel.bin; bootm 0x82000000

3. Once booted, use LuCI sysupgrade to
flash openwrt-ath79-nand-netgear_pgzng1-squashfs-sysupgrade.bin

MAC Table:
WAN (eth0): xx:xa - caldata 0x0
LAN (eth1): xx:xb - caldata 0x6
WLAN (phy0): xx:xc - burned into ath9k caldata

Not Working:
Z-Wave
RS422

Signed-off-by: Chris Blake <chrisrblake93@gmail.com>
(added more hw-info, fixed file permissions)
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>