[SCSI] mpt2sas: Added expander phy control support

Added support to send link resets, hard resets, enable/disable phys, and
changing link rates for for expanders.  This will be exported to
attributes within the sas transport layer.  A new wrapper function was
added for sending SMP passthru to expanders for phy control.

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