f_decoder_wrapper: change video-codec to show description or name

Not both of them. Formating it as `<name> (<desc>)` produced arguably
silly string like `hevc (HEVC (High Efficiency Video Coding))`. Unpack
this to show only description if available or name otherwise. Produces
way nicer results in stats.lua and similar places where this name is
printed.

DOCS/interface-changes.rst

@@ -99,6 +99,7 @@ Interface changes
     - deprecate `--demuxer-cue-codepage` in favor of `--metadata-codepage`
     - change the default of `metadata-codepage` to `auto`
     - add `playlist-next-playlist` and `playlist-prev-playlist` commands
+    - change `video-codec` to show description or name, not both
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

filters/f_decoder_wrapper.c

@@ -450,8 +450,8 @@ static bool reinit_decoder(struct priv *p)
         p->decoder = driver->create(p->decf, p->codec, sel->decoder);
         if (p->decoder) {
             pthread_mutex_lock(&p->cache_lock);
-            p->decoder_desc =
-                talloc_asprintf(p, "%s (%s)", sel->decoder, sel->desc);
+            const char *d = sel->desc && sel->desc[0] ? sel->desc : sel->decoder;
+            p->decoder_desc = talloc_strdup(p, d);
             MP_VERBOSE(p, "Selected codec: %s\n", p->decoder_desc);
             pthread_mutex_unlock(&p->cache_lock);
             break;