scripts: Fix return value checks from subprocess.call()'s

scripts: Fix return value checks from subprocess.call()'s

Python function subprocess.call() returns the return value of the
executed process. If return values are not checked, errors may
go unnoticed and bad things can happen.

Change all callers of subprocess.call() which do not check for
the return value to use subprocess.check_call() which raises
CalledProcessError if the subprocess returns with non-zero value.

https://docs.python.org/2/library/subprocess.html#using-the-subprocess-module

All users of the function were found with:

$ git grep "subprocess\.call" | \
  egrep -v 'if.*subprocess\.call|=\ +subprocess\.call|return.*subprocess\.call'

Tested similar patch on top of yocto jethro. Only compile tested
core-image-minimal on poky master branch.

Signed-off-by: Mikko Rapeli <mikko.rapeli@bmw.de>
Signed-off-by: Ross Burton <ross.burton@intel.com>