util: Use /usr/bin/env as wrapper to look up python

This way users are not constrained to have it installed as
/usr/bin/python.

Change-Id: I822b6c402004aad8f2353e71afbd8ee3f9d26d45
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/13285
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/dtd_parser/dtd_parser.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # dtd_parser.py - DTD structure parser
 #
 # Copyright (C) 2012 The ChromiumOS Authors.  All rights reserved.

util/ipqheader/ipqheader.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # Copyright (c) 2013 The Linux Foundation. All rights reserved.
 #

util/ipqheader/mbncat.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2014, The Linux Foundation. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without

util/optionlist/kconfig2wiki

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # kconfig2wiki - Kconfig to MediaWiki converter for
 # http://www.coreboot.org/Coreboot_Options