net: phy: fixed_phy: remove setting supported/advertised modes from fixed_phy_register

net: phy: fixed_phy: remove setting supported/advertised modes from fixed_phy_register

This code was added with 34b31da486a5 ("phy: fixed_phy: Set supported
speed in phydev") 10 yrs ago. The commit message of this change
mentions a use case involving callback adjust_link of struct
dsa_switch_driver. This struct doesn't exist any longer, and in general
usage of the legacy fixed PHY has been removed from DSA with the switch
to phylink.

Note: Supported and advertised modes are now set by phy_probe() when
the fixed PHY is attached to the netdev and bound to the genphy driver.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/3abaa3c5-fbb9-4052-9346-6cb096a25878@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>