h264dec: rename flush_dpb()

The name is misleading, this function does a lot more than just flushing
the DPB.

libavcodec/h264dec.c

@@ -487,8 +487,7 @@ void ff_h264_flush_change(H264Context *h)
     h->mmco_reset = 1;
 }
 
-/* forget old pics after a seek */
-static void flush_dpb(AVCodecContext *avctx)
+static void h264_decode_flush(AVCodecContext *avctx)
 {
     H264Context *h = avctx->priv_data;
     int i;
@@ -1065,7 +1064,7 @@ AVCodec ff_h264_decoder = {
                            },
     .caps_internal         = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_EXPORTS_CROPPING |
                              FF_CODEC_CAP_ALLOCATE_PROGRESS,
-    .flush                 = flush_dpb,
+    .flush                 = h264_decode_flush,
     .update_thread_context = ONLY_IF_THREADS_ENABLED(ff_h264_update_thread_context),
     .profiles              = NULL_IF_CONFIG_SMALL(ff_h264_profiles),
     .priv_class            = &h264_class,