mutex: add __fio_mutex_remove()

We have to remember to free the condvar, so add a __fio_mutex_remove()
for cases that init a mutex inside an smalloc'ed region with
__fio_mutex_init().

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/mutex.h b/mutex.h
index 246afee..17380de 100644
--- a/mutex.h
+++ b/mutex.h
@@ -26,6 +26,7 @@
 
 extern int __fio_mutex_init(struct fio_mutex *, int);
 extern struct fio_mutex *fio_mutex_init(int);
+extern void __fio_mutex_remove(struct fio_mutex *);
 extern void fio_mutex_remove(struct fio_mutex *);
 extern void fio_mutex_up(struct fio_mutex *);
 extern void fio_mutex_down(struct fio_mutex *);