[SCSI] libfc:prevent dereferencing ERR_PTR in fc_tm_done()

If we goto out, then it tries to call kfree_skb() on an ERR_PTR which
will oops.  Just return directly.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>