mlxsw: spectrum_fid: Add an op for packing SFMR

The way SFMR is packed differs between the controlled and CFF flood modes.
Add an op to dispatch it dynamically.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/f12fe7879a7086ee86343ee4db02c859f78f0534.1701183892.git.petrm@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>