[ALSA] AdLib FM card driver

Attached you'll find an ALSA driver for AdLib FM cards. An AdLib card is
just an OPL2, which was already supported by sound/drivers/opl3, so only
very minimal bus-glue is needed. The patch applies cleanly to both
2.6.16 and 2.6.16-mm1.

The driver has been tested with an actual ancient 8-bit ISA AdLib card
and works fine. It also works fine for an OPL3 {,emulation} as still
found on many ISA soundcards but given that AdLib cards don't have their
own mixer, upping the volume from 0 might be a problem without the card
driver already loaded and driving the OPL3.

Signed-off-by: Takashi Iwai <tiwai@suse.de>