bmips: add support for NuCom R5010UNv2

bmips: add support for NuCom R5010UNv2

The NuCom R5010UNv2 is a wifi fast ethernet router, 2.4 GHz single band
with two external antennas.

Hardware:
 - SoC: Broadcom BCM6328
 - CPU: single core BMIPS4350 V7.5 @ 320Mhz
 - RAM: 64 MB DDR2
 - Flash: 16 MB SPI NOR
 - Ethernet LAN: 4x 100Mbit
 - Wifi 2.4 GHz: Broadcom BCM43217 802.11bgn (onboard)
 - USB: 1x 2.0
 - Buttons: 2x
 - ADSL: yes, unsupported
 - LEDs: 7x
 - UART: yes

Installation via CFE web UI:
  1. Power off the router and press the RESET button
  2. Power on the router and wait 12 or more seconds
  3. Release the RESET button
  4. Browse to http://192.168.1.1 and upload the Openwrt cfe firmware
  5. Wait a few minutes for it to finish

Signed-off-by: Daniel González Cabanelas <dgcbueu@gmail.com>
(cherry picked from commit 6cb3328b4fd4939f3800d4be9d52744b753de1b6)