[SCSI] fc class: fix fc_transport_init error handling

If transport_class_register fails we should unregister any
registered classes, or we will leak memory or other
resources.

I did a quick modprobe of scsi_transport_fc to test the
patch.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>