IB/rdmavt: Remove duplicated functions

The free_qpn() function from the hfi1/qib driver which was the basis for
rdmavt_free_qpn() function was accidentally left in the code. Remove it.

Reviewed-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>