net: phy: phy_caps: Move __set_linkmode_max_speed to phy_caps

Convert the __set_linkmode_max_speed to use the link_capabilities array.
This makes it easy to clamp the linkmodes to a given max speed.
Introduce a new helper phy_caps_linkmode_max_speed to replace the
previous one that used phy_settings.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250307173611.129125-5-maxime.chevallier@bootlin.com


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