decoder/DsdLib: raise ID3 tag limit to 1 MB

A bug report was submitted with a 600 kB ID3 tag that could not be
read by MPD.

src/decoder/plugins/DsdLib.cxx

@@ -125,7 +125,7 @@ dsdlib_tag_id3(InputStream &is,
 
 	const id3_length_t count = size - offset;
 
-	if (count < 10 || count > 256*1024)
+	if (count < 10 || count > 1024 * 1024)
 		return;
 
 	id3_byte_t *const id3_buf = static_cast<id3_byte_t*>(xalloc(count));