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: c48c9f7ff32b ("staging: exfat: add exfat filesystem code to staging")
Signed-off-by: Colin Ian King <[e-mail]>
Cc: Valdis Kletnieks <[e-mail]>,
Reviewed-by: Nathan Chancellor <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/exfat/exfat_super.c

···
 {
 	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;