Add back legacy deviceTypesToString function.

Legacy prebuilt HALs may use this function. Add it back to avoid symbol
loading error.

Bug: 210916964
Test: manual test, audio could be heard.
Change-Id: Ic393688d144e3fdd4e33e8f31bd1e66ce30b2dd1
diff --git a/media/libaudiofoundation/AudioContainers.cpp b/media/libaudiofoundation/AudioContainers.cpp
index 117d188..553a319 100644
--- a/media/libaudiofoundation/AudioContainers.cpp
+++ b/media/libaudiofoundation/AudioContainers.cpp
@@ -89,6 +89,11 @@
     return ss.str();
 }
 
+bool deviceTypesToString(const DeviceTypeSet &deviceTypes, std::string &str) {
+    str = deviceTypesToString(deviceTypes);
+    return true;
+}
+
 std::string dumpDeviceTypes(const DeviceTypeSet &deviceTypes) {
     std::stringstream ss;
     for (auto it = deviceTypes.begin(); it != deviceTypes.end(); ++it) {