__usec_sleep() really just spins, rename it

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/time.c b/time.c
index e84fb01..643fcea 100644
--- a/time.c
+++ b/time.c
@@ -78,7 +78,7 @@
 /*
  * busy looping version for the last few usec
  */
-void __usec_sleep(unsigned int usec)
+void usec_spin(unsigned int usec)
 {
 	struct timeval start;
 
@@ -96,7 +96,7 @@
 		unsigned long ts = usec;
 
 		if (usec < ns_granularity) {
-			__usec_sleep(usec);
+			usec_spin(usec);
 			break;
 		}