hal: fix resource leak issues in platform.c

- fix resource leak issues related to mixer
  controls and file handles

Change-Id: I3675da4504a93a084ad582e5e6eb7c75f38e736e
diff --git a/hal/msm8916/platform.c b/hal/msm8916/platform.c
index 4839451..7cdfc62 100644
--- a/hal/msm8916/platform.c
+++ b/hal/msm8916/platform.c
@@ -1677,6 +1677,7 @@
                 ALOGE("%s: Failed to init audio route controls, aborting.",
                        __func__);
                 free(my_data);
+                mixer_close(adev->mixer);
                 return NULL;
             }
             adev->snd_card = snd_card_num;
@@ -1686,6 +1687,7 @@
         }
         retry_num = 0;
         snd_card_num++;
+        mixer_close(adev->mixer);
     }
 
     if (snd_card_num >= MAX_SND_CARD) {