scripts: Check all CONFIG_* in the code are defined into a Kconfig file

checkConfig script scans all '*.c', '*.h' and '*.S' looking for all
kconfig items used into the Zephyr Code and validates if they are
defined into any '*.kconfig' file.

to execute script use:
*to run with default values:
	$ checkconfig.py
*to run and get complete log of all symbols used:
	$ checkconfig.py -c
*to run from a diferent subdirectory, not zephyr base, like
 drivers/grove
	$ checkconfig.py -s drivers/grove
*to run and exclude some directories for verification:
	$checkconfig.py -e drivers

*to get more help about how to run script:
	$checkconfig.py --help

Change-Id: Ia8ddda8b560305eb73224c55645729a40fcb5863
Signed-off-by: Sonia Leon Bautista <sonia.leon.bautista@intel.com>