ipq40xx: Add support for Linksys MR8300 (Dallas)

ipq40xx: Add support for Linksys MR8300 (Dallas)

The Linksys MR8300 is based on QCA4019 and QCA9888
and provides three, independent radios.
NAND provides two, alternate kernel/firmware images
with fail-over provided by the OEM U-Boot.

Hardware Highlights:

SoC: IPQ4019 at 717 MHz (4 CPUs)
RAM: 512MB RAM

SoC:	Qualcomm IPQ4019 at 717 MHz (4 CPUs)
RAM:	512M DDR3
FLASH:	256 MB NAND (Winbond W29N02GV, 8-bit parallel)
ETH:	Qualcomm QCA8075 (4x GigE LAN, 1x GigE Internet Ethernet Jacks)
BTN:	Reset and WPS
USB:	USB3.0, single port on rear with LED
SERIAL:	Serial pads internal (unpopulated)
LED:	Four status lights on top + USB LED
WIFI1:	2x2:2 QCA4019 2.4 GHz radio on ch. 1-14
WIFI2:  2x2:2 QCA4019 5 GHz radio on ch. 36-64
WIFI3:  2x2:2 QCA9888 5 GHz radio on ch. 100-165

Support is based on the already supported EA8300.
Key differences:
	EA8300 has 256MB RAM where MR8300 has 512MB RAM.
	MR8300 has a revised top panel LED setup.

Installation:
"Factory" images may be installed directly through the OEM GUI using
URL: https://ip-of-router/fwupdate.html (Typically 192.168.1.1)

Signed-off-by: Hans Geiblinger <cybrnook2002@yahoo.com>
[copied Hardware-highlights from EA8300. Fixed alphabetical order.
fixed commit subject, removed bogus unit-address of keys,
fixed author (used Signed-off-By to From:) ]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>