sfc: convert references to LRO to GRO

This driver now uses Generic Receive Offload, not the older LRO.
Change references to LRO in names and comments.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>