[SCSI] mpt fusion: SAS topology scan changes, expander events

SAS topology scan is restructured. HBA firmware is generating more
events. Expander Events are added, Link status events are also added with
respect to SAS topology scan optimization.

Signed-off-by: Kashyap Desai <kadesai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>