This patch adds the Netduino 2 Machine.

This is a Cortex-M3 based machine. Information can be found at:
http://www.netduino.com/netduino2/specs.htmSigned-off-by: NAlistair Francis <alistair@alistair23.me>
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 5bd999824f14252c122c4501cc973cee986eadd7.1424175342.git.alistair@alistair23.me
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>