On kernels using retpoline as a spectrev2 mitigation,
optimize actions and filters that are compiled as built-ins into a direct call.

On subsequent patches we expose the classifiers and actions functions
and wire up the wrapper into tc.
Signed-off-by: NPedro Tammela <pctammela@mojatatu.com>
Reviewed-by: NJamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: NVictor Nogueira <victor@mojatatu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>