net: ethtool: Export the link_mode_params definitions

link_mode_params contains a lookup table of all 802.3 link modes that
are currently supported with structured data about each mode's speed,
duplex, number of lanes and mediums.

As a preparation for a port representation, export that table for the
rest of the net stack to use.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250307173611.129125-2-maxime.chevallier@bootlin.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>