mlxsw: spectrum_acl: Split entry struct into entry and ventry

Do the split of entry struct so the new entry struct is related to the
actual HW entry, whereas ventry struct is a SW abstration of that.
This split prepares possibility for ventry to hold 2 HW entries which
is needed for region ERP rehash flow.

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>