staging: exfat: fix uninitialized variable ret

Currently there are error return paths in ffsReadFile that
exit via lable err_out that return and uninitialized error
return in variable ret. Fix this by initializing ret to zero.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: c48c9f7f ("staging: exfat: add exfat filesystem code to staging")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>,
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lore.kernel.org/r/20190830184644.15590-1-colin.king@canonical.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/exfat_super.c

@@ -779,7 +779,7 @@ static int ffsReadFile(struct inode *inode, struct file_id_t *fid, void *buffer,
 {
 	s32 offset, sec_offset, clu_offset;
 	u32 clu;
-	int ret;
+	int ret = 0;
 	sector_t LogSector;
 	u64 oneblkread, read_bytes;
 	struct buffer_head *tmp_bh = NULL;