ARM: dts: BCM5301X: Add DT for Meraki MR26

ARM: dts: BCM5301X: Add DT for Meraki MR26

Meraki MR26 is an EOL wireless access point featuring a
PoE ethernet port and two dual-band 3x3 MIMO 802.11n
radios and 1x1 dual-band WIFI dedicated to scanning.

Thank you Amir for the unit and PSU.

Hardware info:
SOC   : Broadcom BCM53015A1KFEBG (dual-core Cortex-A9 CPU at 800 MHz)
RAM   : SK Hynix Inc. H5TQ1G63EFR, 1 GBit DDR3 SDRAM = 128 MiB
NAND  : Spansion S34ML01G100TF100, 1 GBit SLC NAND Flash = 128 MiB
ETH   : 1 GBit Ethernet Port - PoE (TPS23754 PoE Interface)
WIFI0 : Broadcom BCM43431KMLG, BCM43431 802.11 abgn (3x3:3)
WIFI1 : Broadcom BCM43431KMLG, BCM43431 802.11 abgn (3x3:3)
WIFI2 : Broadcom BCM43428 "Air Marshal" 802.11 abgn (1x1:1)
BUTTON: One reset key behind a small hole next to the Ethernet Port
LEDS  : One amber (fault), one white (indicator) LED, separate RGB-LED
MISC  : Atmel AT24C64 8KiB EEPROM i2c
      : Ti INA219 26V, 12-bit, i2c output current/voltage/power monitor

SERIAL:
      WARNING: The serial port needs a TTL/RS-232 3V3 level converter!
      The Serial setting is 115200-8-N-1. The board has a populated
      right angle 1x4 0.1" pinheader.
      The pinout is: VCC (next to J3, has the pin 1 indicator), RX, TX, GND.

Odd stuff:

- uboot does not support lzma compression, but gzip'd uImage/DTB work.
- uboot claims to support FIT, but fails to pass the DTB to the kernel.
  Appending the dtb after the kernel image works.
- RGB-controller is supported through an external userspace program.
- The ubi partition contains a "board-config" volume. It stores the
  MAC Address (0x66 in binary) and Serial No. (0x7c alpha-numerical).
- SoC's temperature sensor always reports that it is on fire.
  This causes the system to immediately shutdown! Looking at reported
  "418 degree Celsius" suggests that this sensor is not working.

WIFI:
b43 is able to initialize all three WIFIs @ 802.11bg.
| b43-phy0: Broadcom 43431 WLAN found (core revision 29)
| bcma-pci-bridge 0000:01:00.0: bus1: Switched to core: 0x812
| b43-phy0: Found PHY: Analog 9, Type 7 (HT), Revision 1
| b43-phy0: Found Radio: Manuf 0x17F, ID 0x2059, Revision 0, Version 1
| b43-phy0 warning: 5 GHz band is unsupported on this PHY
| b43-phy1: Broadcom 43431 WLAN found (core revision 29)
| bcma-pci-bridge 0001:01:00.0: bus2: Switched to core: 0x812
| b43-phy1: Found PHY: Analog 9, Type 7 (HT), Revision 1
| b43-phy1: Found Radio: Manuf 0x17F, ID 0x2059, Revision 0, Version 1
| b43-phy1 warning: 5 GHz band is unsupported on this PHY
| b43-phy2: Broadcom 43228 WLAN found (core revision 30)
| bcma-pci-bridge 0002:01:00.0: bus3: Switched to core: 0x812
| b43-phy2: Found PHY: Analog 9, Type 4 (N), Revision 16
| b43-phy2: Found Radio: Manuf 0x17F, ID 0x2057, Revision 9, Version 1
| Broadcom 43xx driver loaded [ Features: NL ]

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>