ALSA: hdspm - Introduce generic AIO tristate control

AIO cards offer at least four individual settings options with three
states each. Those settings are represented as two bits in the settings
register with the following meaning:

   0*some_base_bit --> Option value 0
   1*some_base_bit --> Option value 1
   2*some_base_bit --> Option value 2
   3*some_base_bit --> mask to select the two involved bits

This patch adds a generic ALSA control macro for such a value-to-bit
pattern mapping. It will be used in a later commit to expose four new
controls.

Signed-off-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>