checkpatch: Fix running out of coreboot's tree

* Fix up tree detection to work in a coreboot tree
* Switch C99_COMMENT from ERR to CHK

Change-Id: Ie8d6d1407853b77a4b3e9763f23481bd9402bc61
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/8418
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed