Build: Separate Kconfig system from CMake config system

The Kconfig system now has a separated routine rather than integrated
into the CMake Config system.
It is now easy to adjust the config steps for the Kconfig system without
impacting the CMake system.

Change-Id: I41e088a571448ab74ab9e669d73a623bc9af5e51
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
4 files changed