flow_offload: rename exts stats update functions with hw

Rename exts stats update functions with hw for readability.

We make this change also to update stats from hw for an action
when it is offloaded to hw as a single action.

Signed-off-by: Baowen Zheng <baowen.zheng@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>