mlxsw: core_acl_flex_actions: Add police action

Add core functionality required to support police action in the policy
engine.

The utilized hardware policers are stored in a hash table keyed by the
flow action index. This allows to support policer sharing between
multiple ACL rules.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>