amd-xgbe: Prepare for introduction of clause 37 autoneg

Prepare for the future introduction of clause 37 auto-negotiation by
updating the current auto-negotiation related functions to identify
them as clause 73 functions. Move interrupt enablement to the
enable/disable auto-negotiation functions. Update what will be common
routines to check for the current type of AN and process accordingly.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>