net: dcb: application priority is per net_device

The app_data priority may not be the same for all net devices.
In order for stacks with application notifiers to identify the
specific net device dcb_app_type should be passed in the ptr.

This allows handlers to use dev_get_by_name() to pin priority
to net devices.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>