gpio: move gpio_cmsdk_ahb.h from drivers to include/drivers

Move gpio_cmsdk_ahb.h out of drivers/gpio and into include/drivers/gpio.
This is used by few board files so it should be in include.

This allows to remove few odd
"zephyr_library_include_directories(${ZEPHYR_BASE}/drivers)".

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>