Implement attaching and detaching SF port representor. It is done in the
same way as the VF port representor.

SF port representor is always added or removed with devlink
lock taken.
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>