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/dump/main.c b/exfat/dump/main.c
index b6e0409..3ed3d8f 100644
--- a/exfat/dump/main.c
+++ b/exfat/dump/main.c
@@ -106,7 +106,7 @@
 
 static void dump_sectors(struct exfat* ef)
 {
-	off_t a = 0, b = 0;
+	loff_t a = 0, b = 0;
 
 	printf("Used sectors ");
 	while (exfat_find_used_sectors(ef, &a, &b) == 0)