wlan: Get the net_device properly based on kernel version

linkup_event_var event is not set as part of
hdd_netdev_notifier_call that gets invoked for
NETDEV_CHANGE event due to device name check
failure.

Fix is to get the net_device appropriately either
directly or from the notifier_info based on kernel
version.

Change-Id: I4fc172138b319e2522283dc8e4a785afc076dc04
CRs-Fixed: 2508165