drivers: flash: SoC KSDK

This KSDK flash shim driver supports the device in the FRDM K64F
platform (enabled with this commit).

WARNING: the driver disables the system interrupts for potentially
long periods of time. This is required to avoid Read-While-Write
issues since most platforms run in XIP mode.

For more detailed information see the link below:
http://cache.freescale.com/files/32bit/doc/app_note/AN4695.pdf



Change-Id: I70f8d09080251033ce2f45be0c2eb95c19fded08
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>