audio: Print error in case of nonexistant mixer paths

Change-Id: I131ed6518ce8f26638a3490ee1be7a5d93b4e5b8
(cherry picked from commit 0524e26d2a1d155ce1dc9609b8e8741fd5f1500f)

audio/audio_hw.c

@@ -540,6 +540,11 @@ static int mixer_init(struct audio_device *adev)
             } while (mixer == NULL);
 
             sprintf(mixer_path, "/system/etc/mixer_paths_%d.xml", card);
+            if (access(mixer_path, F_OK) == -1) {
+                ALOGE("%s: Failed to load mixer paths from %s, your system is going to crash",
+                      __func__, mixer_path);
+            }
+
             audio_route = audio_route_init(card, mixer_path);
             if (!audio_route) {
                 ALOGE("%s: Failed to init audio route controls for card %d, aborting.",