net: phy: remove function stubs

net: phy: remove function stubs

All callers of these functions depend on PHYLIB or select it directly
or indirectly by selecting PHYLINK. Stubs make sense for optional
functionality, but that's not the case here.

MDIO_XGENE usually is selected by NET_XGENE which also selects PHYLIB.
Add a dependency to PHYLIB nevertheless, in order not to break
randconfig builds.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/f7a69a1f-60e9-4ac0-8b7c-481e0cc850e7@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>