examples/qsvdec: do not free the surfaces in the frame_free() callback

Even though libmfx might not need them anymore, avcodec might still
access the surfaces. So free them separately at the end.

doc/examples/qsvdec.c

@@ -116,15 +116,6 @@ fail:
 
 static mfxStatus frame_free(mfxHDL pthis, mfxFrameAllocResponse *resp)
 {
-    DecodeContext *decode = pthis;
-
-    if (decode->surfaces)
-        vaDestroySurfaces(decode->va_dpy, decode->surfaces, decode->nb_surfaces);
-    av_freep(&decode->surfaces);
-    av_freep(&decode->surface_ids);
-    av_freep(&decode->surface_used);
-    decode->nb_surfaces = 0;
-
     return MFX_ERR_NONE;
 }
 
@@ -144,6 +135,16 @@ static mfxStatus frame_get_hdl(mfxHDL pthis, mfxMemId mid, mfxHDL *hdl)
     return MFX_ERR_NONE;
 }
 
+static void free_surfaces(DecodeContext *decode)
+{
+    if (decode->surfaces)
+        vaDestroySurfaces(decode->va_dpy, decode->surfaces, decode->nb_surfaces);
+    av_freep(&decode->surfaces);
+    av_freep(&decode->surface_ids);
+    av_freep(&decode->surface_used);
+    decode->nb_surfaces = 0;
+}
+
 static void free_buffer(void *opaque, uint8_t *data)
 {
     int *used = opaque;
@@ -467,6 +468,8 @@ finish:
 
     av_frame_free(&frame);
 
+    free_surfaces(&decode);
+
     if (decode.mfx_session)
         MFXClose(decode.mfx_session);
     if (decode.va_dpy)