net/sched: act_mirred: Add helper function tcf_mirred_replace_dev

The act of replacing a device will be repeated by the init logic for the
block ID in the patch that allows mirred to a block. Therefore we
encapsulate this functionality in a function (tcf_mirred_replace_dev) so
that we can reuse it and avoid code repetition.

Co-developed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Co-developed-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>