tinycap: Modify capture_sample()for pcm data to frames

Test: Without "Captured 0 frames" when generate wav file.

Change-Id: I4d1e08a7ae7d5e43a5415d812506dd1a783ac4cf
diff --git a/tinycap.c b/tinycap.c
index cea98a1..b0c1908 100644
--- a/tinycap.c
+++ b/tinycap.c
@@ -200,6 +200,7 @@
     char *buffer;
     unsigned int size;
     unsigned int bytes_read = 0;
+    unsigned int frames = 0;
     struct timespec end;
     struct timespec now;
 
@@ -250,7 +251,8 @@
         }
     }
 
+    frames = pcm_bytes_to_frames(pcm, bytes_read);
     free(buffer);
     pcm_close(pcm);
-    return pcm_bytes_to_frames(pcm, bytes_read);
+    return frames;
 }