Fix the link speed passed to iflib_link_state_change() when bringing the link up.
The driver was hardcoding IF_Gbps(100), always reporting 100 Gbps regardless of the
actual negotiated rate. Use the firmware-reported link_info->link_speed (in units of 100 Mbps)
and convert with IF_Mbps(link_info->link_speed * 100) so the OS sees the true link speed.

This corrects interface media reporting (e.g., ifconfig, monitoring) without affecting datapath
behavior.