hal: use 0 as default return value for out_get_render_position

- Initialize default return value of out_get_render_position to
  0(NO_ERROR).
- Default value(NO_ERROR) will be used if timestamp query happens
  before compress driver is opened. Return 0(NO_ERROR) in this case
  to avoid playback failures.

Change-Id: I0f8b2e0f19cfe736a19934ddef18016599ec582c
CRs-Fixed: 756508
diff --git a/hal/audio_hw.c b/hal/audio_hw.c
index 9e841df..80fb83b 100644
--- a/hal/audio_hw.c
+++ b/hal/audio_hw.c
@@ -2028,7 +2028,7 @@
 {
     struct stream_out *out = (struct stream_out *)stream;
     if (is_offload_usecase(out->usecase) && (dsp_frames != NULL)) {
-        ssize_t ret =  -EINVAL;
+        ssize_t ret = 0;
         *dsp_frames = 0;
         pthread_mutex_lock(&out->lock);
         if (out->compr != NULL) {