Checkpatch: Various fixes

* Fix sed behaviour so that it can run on more stricter versions (i.e. BSD)
* Fix ambiguous redirection to empty output file
* Improve prints from the script

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: I6db4bbea79d33e8426dd3b04b621e5120bd71588
1 file changed