blk-mq/debugfs: Fix improper print qualifier

struct blk_rq_stat::mean is a u64 value, so use %llu
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-debugfs.c

@@ -17,7 +17,7 @@
 static void print_stat(struct seq_file *m, struct blk_rq_stat *stat)
 {
 	if (stat->nr_samples) {
-		seq_printf(m, "samples=%d, mean=%lld, min=%llu, max=%llu",
+		seq_printf(m, "samples=%d, mean=%llu, min=%llu, max=%llu",
 			   stat->nr_samples, stat->mean, stat->min, stat->max);
 	} else {
 		seq_puts(m, "samples=0");