dca: set output buffer size correctly (fixes #6509, fixes #7459)

Some filters and outputs rely on the samples count (which was correct),
others on the bytes size (which was not), accounting for why decoding
failed only in some combinations.
(cherry picked from commit 244a35b0301164f753a381f569181c6bd3419ad1)

modules/audio_filter/converter/dtstofloat32.c

@@ -315,6 +315,7 @@ static block_t *Convert( filter_t *p_filter, block_t *p_in_buf )
         }
     }
 
+    p_out_buf->i_buffer = p_in_buf->i_nb_samples * 4 * p_sys->i_nb_channels;
     p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
     p_out_buf->i_dts = p_in_buf->i_dts;
     p_out_buf->i_pts = p_in_buf->i_pts;