mlxsw: spectrum: Move ACL flexible actions instance to spectrum

A flexible action instance allows, given a set of ops, creating, committing
and sharing a set of ACL action blocks. The flexible action instance in
question is using the spectrum KVD linear space to store the flexible
action sets.

Move this flexible action instance to the common spectrum struct to allow
other users (such as multicast router) to get that functionality.

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