amd-xgbe: Add additional stats to be reported via ethtool

Add additional/extended statistics beyond what is provided by the
hardware to be reported via ethtool. The new stats focus on the
calls into ndo_start_xmit and the napi_poll routine.

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