sfc: expose CTPIO stats on NICs that support them

While the Linux driver doesn't use CTPIO ('cut-through programmed I/O'),
 other drivers on the same port might, so if we're responsible for
 reporting per-port stats we need to include the CTPIO stats.

Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>