amd-xgbe: Update TSO packet statistics accuracy

When transmitting a TSO packet, the driver only increments the TSO packet
statistic by one rather than the number of total packets that were sent.
Update the driver to record the total number of packets that resulted from
TSO transmit.

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