dpaa2-switch: reuse dpaa2_switch_acl_entry_add() for STP frames trap

Since we added the dpaa2_switch_acl_entry_add() function in the previous
patches to hide all the details of actually adding the ACL entry by
issuing a firmware command, let's use it also for adding a CPU trap for
the STP frames.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>