omxil: Don't free the sentinel buffers

These buffers aren't known to the actual OMX codec.

Normally, these buffers are removed from the queue by
DecodeAudio/DecodeVideo, but if they're pushed multiple
times (which happens when using google sw decoders),
PortReconfigure might try to free them.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit 6643ac0ae02a61c95b3911b1c36856ace0d06b2e)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/codec/omxil/omxil.c

@@ -580,6 +580,8 @@ static OMX_ERRORTYPE DeinitialiseComponent(decoder_t *p_dec,
             for(j = 0; j < p_port->i_buffers; j++)
             {
                 OMX_FIFO_GET(&p_port->fifo, p_buffer);
+                if (p_buffer == &p_sys->sentinel_buffer)
+                    continue;
                 omx_error = OMX_FreeBuffer( omx_handle,
                                             p_port->i_port_index, p_buffer );
 
@@ -1048,6 +1050,8 @@ static OMX_ERRORTYPE PortReconfigure(decoder_t *p_dec, OmxPort *p_port)
     for(i = 0; i < p_port->i_buffers; i++)
     {
         OMX_FIFO_GET(&p_port->fifo, p_buffer);
+        if (p_buffer == &p_sys->sentinel_buffer)
+            continue;
         omx_error = OMX_FreeBuffer( p_sys->omx_handle,
                                     p_port->i_port_index, p_buffer );