idpf: avoid vport access in idpf_get_link_ksettings

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

idpf: avoid vport access in idpf_get_link_ksettings

When the device control plane is removed or the platform

running device control plane is rebooted, a reset is detected

on the driver. On driver reset, it releases the resources and

waits for the reset to complete. If the reset fails, it takes

the error path and releases the vport lock. At this time if the

monitoring tools tries to access link settings, it call traces

for accessing released vport pointer.

To avoid it, move link_speed_mbps to netdev_priv structure

which removes the dependency on vport pointer and the vport lock

in idpf_get_link_ksettings. Also use netif_carrier_ok()

to check the link status and adjust the offsetof to use link_up

instead of link_speed_mbps.