Bluetooth: BR: Add listener cb for discovery

The results of inquiry and extended inquiry
are only reported from application level
after the inquiry complete event notified.

While the event of inquiry result is notified
by controller in real time.

It is not a good user experience.

Just like scanning of LE, add a listener
cb for discovery.

When the event of inquiry result, extended
inquiry result, or remote name request
complete notified, call listener `recv`
cb to notify the upper layer.

When the event of inquiry complete
notified or no pending of remote name
request , call listener `timeout`
cb to notify the upper layer.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>