[SCSI] mpt2sas: Expander fix oops saying "Already part of another port"

Kernel panic is seen because driver did not tear down the port which should
be dnoe using mpt2sas_transport_port_remove(). without this fix When expander
is added back we would oops inside sas_port_add_phy.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>