audio policy: refactor output and input opening

Refactor the way input and output streams are open so that common
logic is centralized in AudioOutputDescriptor and AudioInputDescriptor
classes.

This is in preparation of adding reference counting for ouputs and inputs
opened for a given profile.

Test: Manual
Change-Id: Id806e23077eb41f6398400ab40aeaa694c7d5603
diff --git a/services/audiopolicy/service/AudioPolicyInterfaceImpl.cpp b/services/audiopolicy/service/AudioPolicyInterfaceImpl.cpp
index bd94e3e..1ee5ccf 100644
--- a/services/audiopolicy/service/AudioPolicyInterfaceImpl.cpp
+++ b/services/audiopolicy/service/AudioPolicyInterfaceImpl.cpp
@@ -278,8 +278,8 @@
         return NO_INIT;
     }
     // already checked by client, but double-check in case the client wrapper is bypassed
-    if (attr->source >= AUDIO_SOURCE_CNT && attr->source != AUDIO_SOURCE_HOTWORD &&
-        attr->source != AUDIO_SOURCE_FM_TUNER) {
+    if (attr->source < AUDIO_SOURCE_DEFAULT && attr->source >= AUDIO_SOURCE_CNT &&
+            attr->source != AUDIO_SOURCE_HOTWORD && attr->source != AUDIO_SOURCE_FM_TUNER) {
         return BAD_VALUE;
     }