yocto-bsps: Add a new BSP to support edgerouter

yocto-bsps: Add a new BSP to support edgerouter

  The EdgeRouter Lite is part of the EdgeMax series. It is an MIPS64 router(Cavium Octeon)
  with 512MB of RAM, which uses a USB pendrive for storage.

  Setup instructions
  ------------------

  You will need the following:
  * NFS root setup on your workstation
  * TFTP server installed on your workstation
  * Straight-thru 9-conductor serial cable (DB9, M/F) connected from your
    PC to UART1
  * Ethernet connected to the first ethernet port on the board

The rest of the details can be found in the BSP kernel config, and README.hardware.

Signed-off-by: Yang Wei <Wei.Yang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>