amd-xgbe: Fix SFP PHY supported/advertised settings

When using SFPs, the supported and advertised settings should be initially
based on the SFP that has been detected.  The code currently indicates the
overall support of the device as opposed to what the SFP is capable of.
Update the code to change the supported link modes, auto-negotiation, etc.
to be based on the installed SFP.

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