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/cbm.c b/exfat/mkfs/cbm.c
index 0250571..eb67592 100644
--- a/exfat/mkfs/cbm.c
+++ b/exfat/mkfs/cbm.c
@@ -27,12 +27,12 @@
 #include <limits.h>
 #include <string.h>
 
-static off_t cbm_alignment(void)
+static loff_t cbm_alignment(void)
 {
 	return get_cluster_size();
 }
 
-static off_t cbm_size(void)
+static loff_t cbm_size(void)
 {
 	return DIV_ROUND_UP(
 			(get_volume_size() - get_position(&cbm)) / get_cluster_size(),