Documentation/accounting/getdelays.c: fix endless loop

When no option is passed to getdelays it just hangs, waiting
for a reply which will never come.

This patch prints usage() when no output marker is specified.
Signed-off-by: Marcus Meissner <meissner@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/accounting/getdelays.c

@@ -392,6 +392,10 @@ int main(int argc, char *argv[])
 			goto err;
 		}
 	}
+	if (!maskset && !tid && !containerset) {
+		usage();
+		goto err;
+	}
 
 	do {
 		int i;