When building for a certain platform, we have no idea
what architecture we are building for.
We used to specify the architecture alongside the board or platform
name and this was used to find the defconfig in arch/<arch>/configs.
By putting all board configurations we support in one place we do
not have to specify the architecture, just the configuration name.
Change-Id: Ib7e9f63b9a8051714dc207f583fd26ef620497d8
Signed-off-by: Anas Nashif <anas.nashif@intel.com>