ALSA: usb-audio: scarlett2: Allow bit-level access to config

Add support for accessing configuration values when multiple values
are stored in one byte. Needed by the upcoming Solo and 2i2 Gen 3
support.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/4e54e9e106ec7029c1a668c51b4fc769a7eb4ed0.1624379707.git.g@b4.vu


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