[SCSI] libsas: remove expander from dev list on error

If expander discovery fails (sas_discover_expander()), remove the
expander from the port device list (sas_ex_discover_expander()),
before freeing it. Else the list is corrupted and, e.g., when we
attempt to send SMP commands to other devices, the kernel oopses.

Signed-off-by: Luben Tuikov <ltuikov@yahoo.com>
Cc: stable@kernel.org
Reviewed-by: Jack Wang <jack_wang@usish.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>