openvswitch: Simplify do_execute_actions().

do_execute_actions() implements a worthwhile optimization: in case
an output action is the last action in an action list, skb_clone()
can be avoided by outputing the current skb. However, the
implementation is more complicated than necessary.  This patch
simplify this logic.

Signed-off-by: Andy Zhou <azhou@ovn.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>