audio: Update ChildInterface to set scheduler policy lazily

Since the client may end up never retrieving the interface
instance for sending it over Binder, postpone setting
of the scheduler policy to until that very moment.

Rename 'ChildInterface::getPtr' to 'getInstance' for clarity.

Bug: 264712385
Test: atest VtsHalAudioCoreTargetTest
Change-Id: I31f9dd832c7f85f9632d1d389a8b1063d237d4c1
diff --git a/audio/aidl/default/ModulePrimary.cpp b/audio/aidl/default/ModulePrimary.cpp
index d8ea9e7..29e8126 100644
--- a/audio/aidl/default/ModulePrimary.cpp
+++ b/audio/aidl/default/ModulePrimary.cpp
@@ -37,7 +37,7 @@
     if (!mTelephony) {
         mTelephony = ndk::SharedRefBase::make<Telephony>();
     }
-    *_aidl_return = mTelephony.getPtr();
+    *_aidl_return = mTelephony.getInstance();
     LOG(DEBUG) << __func__
                << ": returning instance of ITelephony: " << _aidl_return->get()->asBinder().get();
     return ndk::ScopedAStatus::ok();