datapath: openvswitch: Refactor recirc key allocation.

datapath: openvswitch: Refactor recirc key allocation.

Upstream commit:
    openvswitch: Refactor recirc key allocation.

    The logic of allocating and copy key for each 'exec_actions_level'
    was specific to execute_recirc(). However, future patches will reuse
    as well.  Refactor the logic into its own function clone_key().

    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>
Upstream: 4572ef52a00b ("openvswitch: Refactor recirc key allocation.")
Signed-off-by: Andy Zhou <azhou@ovn.org>
Acked-by: Joe Stringer <joe@ovn.org>