IB/hfi1: Fix MAD port poll for active cables

A MAD directive to start polling must go through the normal
link tuning and start steps in order to correctly handle
active cables.

Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>