net/mlx5: E-Switch, Allow offloading fwd dest flow table with vport

Before this commit a fwd dest flow table resulted in ignoring vport dests
which is incorrect and is supported.
With this commit the dests can be a mix of flow table and vport dests.
There is still a limitation that there cannot be more than one flow table dest.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>