f_decoder_wrapper: fix initialization state

Some state wasn't reset when decoding was started without a seek reset
before it. The code used to rely on reset_decoder() resetting this
state, but since the commit referenced below, reset_decoder() does less
than reset().

Fix this by explicitly calling reset() on initialization.

Fixes: "f_decoder_wrapper: avoid full reset on timeline switch etc."

filters/f_decoder_wrapper.c

@@ -810,6 +810,8 @@ struct mp_decoder_wrapper *mp_decoder_wrapper_create(struct mp_filter *parent,
         goto error;
     p->demux = demux->pins[0];
 
+    reset(f);
+
     return w;
 error:
     talloc_free(f);