scripts/runqemu: Replace subprocess.run() for compatibilty

scripts/runqemu: Replace subprocess.run() for compatibilty

subprocess.run() was introduced in Python 3.5. We currently support down to
Python 3.4 so I've replaced it with subprocess.check_call() which is available
in that version.

Signed-off-by: Michael Halstead <mhalstead@linuxfoundation.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>