Explicitly ignore return value of __futex_syscall3

Change-Id: Ic65f257bfc4a0eff7bdd3c44fab68a3f17e2bd08
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 77236b9..470b018 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -2760,7 +2760,7 @@
         if (state->mCommand == FastMixerState::COLD_IDLE) {
             int32_t old = android_atomic_inc(&mFastMixerFutex);
             if (old == -1) {
-                __futex_syscall3(&mFastMixerFutex, FUTEX_WAKE_PRIVATE, 1);
+                (void) __futex_syscall3(&mFastMixerFutex, FUTEX_WAKE_PRIVATE, 1);
             }
         }
         state->mCommand = FastMixerState::EXIT;
@@ -2817,7 +2817,7 @@
             if (state->mCommand == FastMixerState::COLD_IDLE) {
                 int32_t old = android_atomic_inc(&mFastMixerFutex);
                 if (old == -1) {
-                    __futex_syscall3(&mFastMixerFutex, FUTEX_WAKE_PRIVATE, 1);
+                    (void) __futex_syscall3(&mFastMixerFutex, FUTEX_WAKE_PRIVATE, 1);
                 }
 #ifdef AUDIO_WATCHDOG
                 if (mAudioWatchdog != 0) {