net: mscc: ocelot: issue a warning if stats are incorrectly ordered

Ocelot uses regmap_bulk_read() operations to efficiently read stats
registers. Currently the implementation relies on the stats layout to be
ordered to be most efficient.

Issue a warning if any future implementations happen to break this pattern.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Co-developed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>