glue: Move nrfx glue code to main Zephyr repository

Update definition of this module so that CMakeLists.txt and Kconfig
for it are taken from external module root (modules/nordic/ in Zephyr).
Move all nrfx related glue files to the modules/nordic/nrfx/ directory
in the main Zephyr repository.

Signed-off-by: Andrzej Głąbek <[email protected]>

Author: anangl