Changed off_t to loff_t

- off_t is long, loff_t is long long (32bit vs. 64bit)
- exfat requites 64 bit to support larger than 2GB fs

Change-Id: I70293e45d7d6686317edc759092e738a2ebdd860
diff --git a/exfat/mkfs/rootdir.c b/exfat/mkfs/rootdir.c
index 84fa31f..33ac3f9 100644
--- a/exfat/mkfs/rootdir.c
+++ b/exfat/mkfs/rootdir.c
@@ -26,12 +26,12 @@
 #include "uctc.h"
 #include <string.h>
 
-static off_t rootdir_alignment(void)
+static loff_t rootdir_alignment(void)
 {
 	return get_cluster_size();
 }
 
-static off_t rootdir_size(void)
+static loff_t rootdir_size(void)
 {
 	return get_cluster_size();
 }