Fix vorbis seeking

Since seeking can return 0 (offset = 0, whence = SEEK_SET), it is
incorrect to return -1 in these cases.

Signed-off-by: mio <stigma@disroot.org>

akode/plugins/xiph_decoder/vorbis_decoder.cpp

@@ -39,10 +39,7 @@ static size_t _read(void *ptr, size_t size, size_t nmemb, void *datasource) {
 
 static int _seek(void *datasource, ogg_int64_t offset, int whence) {
     File *src = (File*)datasource;
-    if (src->lseek(offset, whence))
-        return 0;
-    else
-        return -1;
+    return src->lseek(offset, whence);
 }
 
 static int _close(void *datasource) {