mlxsw: spectrum: acl_erp: Convert to use objagg for tracking ERPs

Currently the ERPs are tracked internally in a hashtable. Benefit from
the newly introduced objagg library and use it to track ERPs. At this
point, there is no nesting of objects done, as the delta_create callback
always returns -EOPNOTSUPP. On the way, add "mask" into ERP mask get and
set functions and struct names.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>