amd-xgbe: Update/fix 2.5GbE support

Update the amd-xgbe driver and phylib driver to better support
the 2.5GbE mode for the hardware. In order to be able establish
2.5GbE using clause 73 auto negotiation the device will support
speed sets of 1GbE/10GbE and 2.5GbE/10GbE.

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