smalloc: fix int truncation issue

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/smalloc.h b/smalloc.h
index 6905c6a..f9a5e41 100644
--- a/smalloc.h
+++ b/smalloc.h
@@ -1,7 +1,7 @@
 #ifndef FIO_SMALLOC_H
 #define FIO_SMALLOC_H
 
-extern void *smalloc(unsigned int);
+extern void *smalloc(size_t);
 extern void sfree(void *);
 extern char *smalloc_strdup(const char *);
 extern void sinit(void);