checkpatch: allow c99 style // comments

Sanitise the lines that contain c99 comments so that the error doesn't
get emitted.

Link: http://lkml.kernel.org/r/d4d22c34ad7bcc1bceb52f0742f76b7a6d585235.1468368420.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -55,6 +55,7 @@ my $spelling_file = "$D/spelling.txt";
 my $codespell = 0;
 my $codespellfile = "/usr/share/codespell/dictionary.txt";
 my $color = 1;
+my $allow_c99_comments = 1;
 
 sub help {
 	my ($exitcode) = @_;
@@ -1144,6 +1145,11 @@ sub sanitise_line {
 		$res =~ s@(\#\s*(?:error|warning)\s+).*@$1$clean@;
 	}
 
+	if ($allow_c99_comments && $res =~ m@(//.*$)@) {
+		my $match = $1;
+		$res =~ s/\Q$match\E/"$;" x length($match)/e;
+	}
+
 	return $res;
 }