IB/hfi1: Use context pointer rather than context index

The hfi1_<set|clear>_ctxt_<j|p>key functions take a context index and
look up the context based on that index.

Since the context index is being retrieved from the context, this
doesn't seem optimal.

Pass the context pointer for use, rather than the context index.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>