checkpatch: fix long line messages about patch context

Changes in ("checkpatch: categorize some long line length checks")
now erroneously reports long line defects in patch context.

Fix it.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2599,7 +2599,7 @@ sub process {
 # if LONG_LINE is ignored, the other 2 types are also ignored
 #
 
-		if ($length > $max_line_length) {
+		if ($line =~ /^\+/ && $length > $max_line_length) {
 			my $msg_type = "LONG_LINE";
 
 			# Check the allowed long line types first