bcm63xx: add support for Innacomm W3400V6

bcm63xx: add support for Innacomm W3400V6

Innacomm W3400V6 is an xDSL B/G wireless router based on Broadcom BCM6328 SoC.

Hardware:
   SoC:          Broadcom BCM6328
   CPU:          BMIPS4350 V8.0, 320 MHz, 1 core
   Flash:        SPI-NOR 8MB, MX25L6406E
   RAM:          64 MB
   Ethernet:     4x 10/100 Mbps
   Switch:       Integrated
   Wireless:     802.11b/g, BCM4312
   LEDs/Buttons: 9x / 2x

Flash instruction, web UI:
1) Set a static IP on your computer compatible
with 192.168.1.1, i.e 192.168.1.100
2) Connect the ethernet cable from your computer to the router.
3) Make sure the router is powered off.
4) Press the reset button, don't release it yet!
5) While pressing reset, power on the router.
6) Wait 10 seconds or more.
Note: The power LED is red at first then turns to solid
green when ready.
8) Release the reset button.
9) Browse to 192.168.1.1
10) Select .bin file.
10) Upgrade the image.
11) Wait for it to reboot.

Signed-off-by: Sieng Piaw Liew <liew.s.piaw@gmail.com>
[Ammend commit description, merge patches, DT improvements]
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>