amd-xgbe: Add ethtool error and debug messages

Add error and dynamic debug messages to various ethtool functions in
the driver while also removing the DBGPR debug print calls. Also, change
the message level for some error messages from alert to err.

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