[ALSA] Add ALSA support for the SEGA Dreamcast PCM device

ALSA support for the SEGA Dreamcast Yamaha AICA sound device (pcm)
This patch adds ALSA sound support for pcm playback on two channels on
the SEGA Dreamcast built-in sound device (the Yamaha AICA)
Add driver for the AICA sound device built into the SEGA Dreamcast
Hook it all up with the build system.

Signed-off-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>