[ALSA] ca0106: Add more symbol SPI register names and use them

Add more symbol name for SPI register values.  Change the SPI_XXX_BIT defines
from the bit number to a mask.  Saves having to write (1<<SPI_XXX_BIT) all the
time to convert to mask.  We never end up wanting the bit number.
Use all the symbol names for the SPI DAC init sequence.  The sequence is
exactly the same as it was before.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>