staging/rdma/hfi1: Load SBus firmware once per ASIC

Using fw_sbus_load to control SBus firmware load doesn't scale across multiple
HFI1 cards in a single system. This patch ensures that the SBus firmware is
loaded once per ASIC.

Reviewed-by: Dean Luick <dean.luick@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>