IB/hfi1: Correctly obtain the full service class

The function hdr2sc was using an unshifted mask to obtain
the 5th bit of the service class.  Correct the issue by using
the shifted mask.

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