net: phy: fixed_phy: remove two function stubs

Remove stubs for fixed_phy_set_link_update() and
fixed_phy_change_carrier() because all callers
(actually just one per function) select config
symbol FIXED_PHY.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/8729170d-cf39-48d9-aabc-c9aa4acda070@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>