- figured out 'Digital(ly) Enhanced Game Port' functionality,
  implemented support for it (eliminating gameport polling overhead)
- removed optional joystick activation, gameport now enabled unconditionally,
  since we now support it via the PCI I/O space, not via conflict-prone
  legacy I/O (which I was thus able to DISABLE now)!
- fix playback bug (a muted wave output would get unmuted upon start of
  playback, of course this is not what we want, thus remember mute state)
- implement partial power management: when idle, lower clock rate and disable
  codec (reduced noise!), and disable gameport circuit when unused
- instantiate OPL3 timer, too
- much better implementation of snd_azf3328_mixer_write_volume_gradually()
- slightly optimized interrupt handling
- lots of cleanup

This time, I also found a way to verify proper OPL3 operation
via MIDI file playback (emulation via synth hardware).
Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>