IB/core: sysfs.c: Fix PerfMgt ClassPortInfo handling

Port number is not part of ClassPortInfo attribute but is
still needed as a parameter when invoking process_mad.

To properly handle this attribute, port_num is added as a
parameter to get_counter_table and get_perf_mad was changed
not to store port_num in the attribute itself when it's
querying the ClassPortInfo attribute.

This handles issue pointed out by Matan Barak <matanb@dev.mellanox.co.il>

Fixes: 145d9c54 ('IB/core: Display extended counter set if available')

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
Acked-by: Matan Barak <matanb@mellanox.com>
Acked-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>