IPoIB: Remove unnecessary port query

There are two queries for port attributes one after another. A second
call is not needed since port_attr structure already holds the data.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>