The last 8 bytes of the buffer list is defined to contain the number
of dropped frames. At the moment we use it to store rx entries,
which trips up ethtool -S:

rx_no_buffer: 9223380832981355136

Fix this by skipping the last buffer list entry.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAlexander Graf <agraf@suse.de>