IB/hfi1: Move serdes tune inside link start function

All calls to tune_serdes and start_link are paired.  Move
tune_serdes inside start_link.

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