octeontx2-pf: CN10K: Hide RPM stats over ethtool

CN10K MAC block (RPM) differs in number of stats compared to Octeontx2
MAC block (CGX). RPM supports stats for each class of PFC and error
packets etc. It would be difficult for user to read stats from ethtool
and map to their definition.

New debugfs file is already added to read RPM stats along with their
definition. This patch adds proper checks such that RPM stats will not
be part of ethtool.

Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>