avcodec/alsdec: Mark decoder as init-threadsafe

It does not initialize any static data in its init function.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/alsdec.c

@@ -2177,5 +2177,5 @@ const AVCodec ff_als_decoder = {
     .decode         = decode_frame,
     .flush          = flush,
     .capabilities   = AV_CODEC_CAP_SUBFRAMES | AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,
-    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
 };