Fix pcm_writei return value if pcm is in not running state.

As per comment, on success, pcm_writei returns the number of frames written.
Fix the case of pcm not running.

Signed-off-by: Miguel GAIO <mgaio35@gmail.com>
diff --git a/src/pcm.c b/src/pcm.c
index 7a67cfe..f665cb4 100644
--- a/src/pcm.c
+++ b/src/pcm.c
@@ -695,7 +695,7 @@
             if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x))
                 return oops(pcm, errno, "cannot write initial data");
             pcm->running = 1;
-            return 0;
+            return x.result;
         }
         if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x)) {
             pcm->prepared = 0;