net/mlx5e: Move representor vnic reporter to eswitch devlink port

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: Move representor vnic reporter to eswitch devlink port

The representor vnic devlink health reporter is created and destroyed
along the representor netdev (un)load path, which is not serialized by
the devlink instance lock. Destroying the reporter from there triggers
a devl_assert_locked() splat on driver unbind:
WARNING: net/devlink/core.c:259 at devl_assert_locked+0x54/0x70, CPU#2: bash/3758
Modules linked in: mlx5_vdpa vringh vdpa mlx5_ib mlx5_fwctl mlx5_core ...
CPU: 2 UID: 0 PID: 3758 Comm: bash Tainted: G W 6.19.0+ #1 PREEMPT
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), ...
RIP: 0010:devl_assert_locked+0x54/0x70
Call Trace:
<TASK>
devl_health_reporter_destroy+0x3a/0x1b0
mlx5e_vport_rep_unload+0x12d/0x2b0 [mlx5_core]
mlx5_eswitch_unregister_vport_reps+0x1b8/0x220 [mlx5_core]
? __esw_offloads_unload_rep+0x190/0x190 [mlx5_core]
? kernfs_remove_by_name_ns+0xc3/0xf0
device_release_driver_internal+0x3b2/0x560
unbind_store+0xce/0xf0

Move the reporter's lifecycle to the eswitch devlink port (un)register
paths, which are already serialized by the devlink instance lock, and
store the handle on mlx5_devlink_port. Use the port's mlx5_vport as the
reporter priv since the diagnose callback only needs a device handle and
a vport number, and mlx5_vport carries both and is initialized before
any representor driver probes.