[SCSI] mpt2sas: Added expander phy counter support

Added support to retrieve the invalid_dword_count,
running_disparity_error_count, loss_of_dword_sync_count, and
phy_reset_problem_count for expanders.  This will be exported to
attributes within the sas transport layer.  A new wrapper function was
added for sending SMP passthru to retrieve the expander phy error log.

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