[SCSI] mpt2sas: Support dev remove when phy status is MPI2_EVENT_SAS_TOPO_PHYSTATUS_VACANT

Add support to process device removal events when the phy status is set to
MPI2_EVENT_SAS_TOPO_PHYSTATUS_VACANT.

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