->getevents() should take unsigned args

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/ioengines.c b/ioengines.c
index d34d2f4..9aacc33 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -165,7 +165,7 @@
 	return 0;
 }
 
-int td_io_getevents(struct thread_data *td, int min, int max,
+int td_io_getevents(struct thread_data *td, unsigned int min, unsigned int max,
 		    struct timespec *t)
 {
 	if (min > 0 && td->io_ops->commit) {