avdevice/decklink_dec: fix stopping streams in read_close

The capture_started variable was never set, it is simpler to call the stop
functions unconditionally if the interface is available.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavdevice/decklink_common.h

@@ -115,7 +115,6 @@ struct decklink_ctx {
 
     /* Status */
     int playback_started;
-    int capture_started;
     int64_t last_pts;
     unsigned long frameCount;
     unsigned int dropped;

libavdevice/decklink_dec.cpp

@@ -983,7 +983,7 @@ av_cold int ff_decklink_read_close(AVFormatContext *avctx)
     struct decklink_cctx *cctx = (struct decklink_cctx *)avctx->priv_data;
     struct decklink_ctx *ctx = (struct decklink_ctx *)cctx->ctx;
 
-    if (ctx->capture_started) {
+    if (ctx->dli) {
         ctx->dli->StopStreams();
         ctx->dli->DisableVideoInput();
         ctx->dli->DisableAudioInput();