checkkconfigsymbols.py: set python2 as default interpreter

Some more recent distributions set the default interpreter to python3,
causing the script to break since it's written for python2.
Signed-off-by: NValentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/checkkconfigsymbols.py

-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 """Find Kconfig symbols that are referenced but not defined."""