dpaa2-switch: install default STP trap rule with the highest priority

Change the default ACL trap rule for STP frames to have the highest
priority.

In the same ACL table will reside both default rules added by the driver
for its internal use as well as rules added with tc flower.  In this
case, the default rules such as the STP one that we already have should
have the highest priority.

Also, remove the check for a full ACL table since we already know that
it's sized so that we don't hit this case.  The last thing changes is
that default trap filters will not be counted in the acl_tbl's num_rules
variable since their number doesn't change.

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