Missed fls() -> __fls() conversion

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/engines/syslet-rw.c b/engines/syslet-rw.c
index 47610a0..4b3e5ef 100644
--- a/engines/syslet-rw.c
+++ b/engines/syslet-rw.c
@@ -242,7 +242,7 @@
 	 */
 	ring_nr = td->o.iodepth;
 	if (ring_nr & (ring_nr - 1))
-		ring_nr = 1 << fls(ring_nr);
+		ring_nr = 1 << __fls(ring_nr);
 
 	ring_size = sizeof(struct syslet_ring) +
 			ring_nr * sizeof(struct syslet_completion);