core/device: Make filtered discovery able to detect beacons

This makes it possible to use SetDiscoveryFilter to disable checking
discoverable flags making it possible to see beacons such as the ones
create by tools/eddystone that doesn't show on regular discovery sessions
since they are not discoverable/connectable.
diff --git a/doc/adapter-api.txt b/doc/adapter-api.txt
index 4dbf879..97462a3 100644
--- a/doc/adapter-api.txt
+++ b/doc/adapter-api.txt
@@ -80,7 +80,11 @@
 
 			When discovery filter is set, Device objects will be
 			created as new devices with matching criteria are
-			discovered. PropertiesChanged signals will be emitted
+			discovered regardless of they are connectable or
+			discoverable which enables listening to
+			non-connectable and non-discoverable devices.
+
+			PropertiesChanged signals will be emitted
 			for already existing Device objects, with updated RSSI
 			value. If one or more discovery filters have been set,
 			the RSSI delta-threshold, that is imposed by
diff --git a/src/adapter.c b/src/adapter.c
index f4fbf82..5499bfc 100644
--- a/src/adapter.c
+++ b/src/adapter.c
@@ -5451,7 +5451,7 @@
 	memset(&eir_data, 0, sizeof(eir_data));
 	eir_parse(&eir_data, data, data_len);
 
-	if (bdaddr_type == BDADDR_BREDR)
+	if (bdaddr_type == BDADDR_BREDR || adapter->filtered_discovery)
 		discoverable = true;
 	else
 		discoverable = eir_data.flags & (EIR_LIM_DISC | EIR_GEN_DISC);