stm32f205: Add the stm32f205 SoC

stm32f205: Add the stm32f205 SoC

This patch adds the stm32f205 SoC. This will be used by the
Netduino 2 to create a machine.

Signed-off-by: Alistair Francis <alistair@alistair23.me>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 48d509747a1ea0d8a7d5480560495e679990f9d2.1424175342.git.alistair@alistair23.me
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>