cmake: export Zephyr modules as Kconfig variables.
cmake: export Zephyr modules as Kconfig variables.

In CMake it is possible to reference each Zephyr module as a CMake
variable. This commit introduces the same feature to Kconfig, so that
it is possible to reference a module in consistent way in both CMake
and Kconfig.

To include a file from module FOO in CMake, use:
include(${ZEPHYR_FOO_MODULE_DIR}/somefile.cmake

To source a file from module FOO in Kconfig, use:
source "$(ZEPHYR_FOO_MODULE_DIR)/Kconfig.somefile"

Signed-off-by: Torsten Rasmussen <a7c5b1d5a1f41fce6edfa3f7c2392ae0c59deafe@nordicsemi.no>

zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr