net/mlx5: Register SF resource on PF port representor

The device-level "resource show" displays max_local_SFs and
max_external_SFs without indicating which port each resource belongs
to. Users cannot determine the controller number and pfnum associated
with each SF pool.

Register max_SFs resource on the host PF representor port to expose
per-port SF limits. Users can correlate the port resource with the
controller number and pfnum shown in 'devlink port show'.

Future patches will introduce an ECPF that manages multiple PFs,
where each PF has its own SF pool.

Example usage:

$ devlink resource show pci/0000:03:00.0/196608
pci/0000:03:00.0/196608:
name max_SFs size 20 unit entry

$ devlink port show pci/0000:03:00.0/196608
pci/0000:03:00.0/196608: type eth netdev pf0hpf flavour pcipf
controller 1 pfnum 0 external true splittable false
function:
hw_addr b8:3f:d2:e1:8f:dc roce enable max_io_eqs 120

We can create up to 20 SFs over devlink port pci/0000:03:00.0/196608,
with pfnum 0 and controller 1.

Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Shay Drori <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260407194107.148063-4-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>