mlxsw: spectrum: Put pointer to flex action ops to mlxsw_sp

Spectrum-2 need a slightly different handling of flexible actions. So
put an ops pointer in mlxsw_sp struct and rename it.

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>