arm: Support for new ARM board FRDM-KL25Z

In order to allow the use of such board, a very preliminar port was
developed. It consists of board files, as well as pinmux, uart, gpio,
spi drivers and device tree files.

Change-Id: I5753064e39e0b023cf4481744c176de26d8dbebb
Signed-off-by: Gustavo Denardin <gustavo.denardin@gmail.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>