P2P: Add new_device flag to dev_found callback

P2P: Add new_device flag to dev_found callback

The DBus code will want to have perfect matching of dev_found and the
dev_lost it adds so it doesn't need to keep track internally. Enable
that with a new flag in the core that tracks whether we have already
notified about this -- the existing users can ignore it.

The part where this is always set to 1 if the new device is discovered
by a driver that has P2P in the driver is buggy -- the driver should
feed the P2P peer database and then that should feed the notification
here instead.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>