boards: Add support for the RedBear nRF51 BLE Nano board

Board uses nRF51822-QFAA, with 16kB of RAM and 256kB of flash.

Change-Id: I92b543022ae6103683cc9e16b925508fb3cf7db1
Signed-off-by: Ricardo Salveti <ricardo.salveti@linaro.org>
6 files changed