amd-xgbe: Separate C22 and C45 transactions

The xgbe MDIO bus driver can perform both C22 and C45 transfers, when
using its MDIO bus hardware. The SFP I2C mdio bus driver only supports
C22. 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>