Define boards based on platforms/SoCs and define them under boards/.
Also unify the naming of all platform, SoC and board files and use
platform.h for platforms and board.h for boards.
Change-Id: Icfeb96479ab5800aca98c80a79bdc3cecd645314
Signed-off-by: Anas Nashif <anas.nashif@intel.com>