Bluetooth: shell: Improve device found event callback

With this patch device name obtained from advertising packets
will be printed out.

[DEVICE]: D0:03:4B:DA:10:46 (public), AD evt type 0,
			RSSI -83 AppleLETester
[DEVICE]: D0:03:4B:DA:10:46 (public), AD evt type 4,
			RSSI -82
[DEVICE]: 00:A0:50:00:00:08 (public), AD evt type 0,
			RSSI -80 BLE Keyboard

Change-Id: Ic5116bce958d5b4479d481c40b2658ab56ecb819
Signed-off-by: Mariusz Skamra <mariusz.skamra@tieto.com>