ethdev: fix adding invalid MAC address

ethdev: fix adding invalid MAC address

Some customers find adding MAC addr to VF sometimes can fail,
but it is still stored in dev->data->mac_addrs[ ]. So this
can lead to some errors that assumes the non-zero entry in
dev->data->mac_addrs[ ] is valid.
Following acknowledgements are from specific NIC PMD
maintainer for their managing part.

This patch changes the ethdev internal API, it should not be
backported to a stable/LTS release so far.

Fixes: af75078fece3 ("first public release")

Signed-off-by: Wei Dai <wei.dai@intel.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: Wenzhuo Lu <wenzhuo.lu@intel.com>