net: phy: phy_caps: Implement link_capabilities lookup by linkmode

In several occasions, phylib needs to lookup a set of matching speed and
duplex against a given linkmode set. Instead of relying on the
phy_settings array and thus iterate over the whole linkmodes list, use
the link_capabilities array to lookup these matches, as we aren't
interested in the actual link setting that matches but rather the speed
and duplex for that setting.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250307173611.129125-7-maxime.chevallier@bootlin.com


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