net/mlx5: E-Switch, Add support for adjacent functions vports discovery

net/mlx5: E-Switch, Add support for adjacent functions vports discovery

Adding driver support to query adjacent functions vports, AKA
delegated vports.

Adjacent functions can delegate their sriov vfs to other sibling PF in
the system, to be managed by the eswitch capable sibling PF.
E.g, ECPF to Host PF, multi host PF between each other, etc.

Only supported in switchdev mode.

Signed-off-by: Adithya Jayachandran <ajayachandra@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250829223722.900629-4-saeed@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>