Revert "libbinder: Replace deprecated utils/threads.h header"

This reverts commit bc8d5b4830d7fb5afe52f9d8809212babedd72b1.

Reason for revert: breaks libvrflinger build

Change-Id: I767dbf3ed56893ead497184d2204a04156faaa9d
diff --git a/libs/binder/BufferedTextOutput.h b/libs/binder/BufferedTextOutput.h
index 57e03cb..fdd532a 100644
--- a/libs/binder/BufferedTextOutput.h
+++ b/libs/binder/BufferedTextOutput.h
@@ -18,8 +18,8 @@
 #define ANDROID_BUFFEREDTEXTOUTPUT_H
 
 #include <binder/TextOutput.h>
+#include <utils/threads.h>
 #include <sys/uio.h>
-#include <utils/Mutex.h>
 
 // ---------------------------------------------------------------------------
 namespace android {