Revert "net: ena: ethtool: add extra properties retrieval via get_priv_flags"

This reverts commit 315c28d2

 ("net: ena: ethtool: add extra properties retrieval via get_priv_flags").

As discussed at netconf and on the mailing list we can't allow
for the the abuse of private flags for exposing arbitrary device
labels.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>