amd-xgbe: Remove the adjustments needed for fixed speed

With the addition of entries in the phy speed/duplex settings
array to support KR and KX mode, the work-around to add/remove
baseT settings to run at a fixed speed is no longer needed.

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