Fix performance-for-range-copy warnings

Bug: 30413223
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,performance*
Change-Id: Ia63c695575d2602ff7e67db874d423b99f4daeef
diff --git a/services/oboeservice/AAudioServiceEndpointMMAP.cpp b/services/oboeservice/AAudioServiceEndpointMMAP.cpp
index f30f9bb..5a429c9 100644
--- a/services/oboeservice/AAudioServiceEndpointMMAP.cpp
+++ b/services/oboeservice/AAudioServiceEndpointMMAP.cpp
@@ -373,7 +373,7 @@
     float volume = values[0];
     ALOGD("%s(%p) volume[0] = %f", __func__, this, volume);
     std::lock_guard<std::mutex> lock(mLockStreams);
-    for(const auto stream : mRegisteredStreams) {
+    for(const auto& stream : mRegisteredStreams) {
         stream->onVolumeChanged(volume);
     }
 };