IB/user_mad: Fix buggy usage of port index

The addition of the rdma_cap_ib_mad is technically broken in ib_umad_remove_one
because the loop "i" value is not a port value.

This bug resulted in the ib_umad failing to properly remove its resources when
the core capability functions were converted to bit fields.

NOTE: e17371d73908 did not result in broken behavior on its own.  It was only
an issue when the implementation of rdma_cap_ib_mad was changed.

Pass the port value to rdma_cap_ib_mad.

Fixes: e17371d73908 ("IB/Verbs: Use management helper rdma_cap_ib_mad()")

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>