net: lan743x: Separate C22 and C45 transactions

The microchip lan743x MDIO bus driver can perform both C22 and C45
transfers in some variants. Create separate functions for each and
register the C45 versions using the new API calls where appropriate.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>