util/lint: Add lint and checkpatch coverage for tests/ dir

Signed-off-by: Jan Dabros <jsd@semihalf.com>
Change-Id: I8018b75844e630c9ed46c8bc48f2aa1634bf3369
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43511
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>

util/lint/lint-007-checkpatch

@@ -22,7 +22,7 @@ opts="--max-line-length 96"
 
 # default: test src and util
 if [ "$1" = "" ]; then
-	INCLUDED_DIRS="src util"
+	INCLUDED_DIRS="src util tests"
 # special mode: take diff from stdin, but exclude the dirs
 elif [ "$1" = "diff" ]; then
 	args=$( echo $EXCLUDED_DIRS | \