[ALSA] sparc dbri: ring buffered version

It is a complete rework of low level layer to work on ring
buffers for comands and data descriptors. This removes annoying
noise due to delay in data buffer switching.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>