audio_mp3: Don't reset self->pos on seek

This is a position in the buffer, it shouldn't be reset.

components/audio_mp3/audio_mp3.c

@@ -144,7 +144,6 @@ static void mp3_think(st3m_media *media, float ms_elapsed) {
     if (self->file && self->control.seek == 0) {
         rewind(self->file);
         self->offset = 0;
-        self->pos = 0;
         self->control.time = 0;
         self->control.position = 0;
         self->control.seek = -1;