ALSA: emu10k1: automate encoding of sub-register definitions

The idea to encode the bitfield manipulation in the register address is
quite clever, but doing that by hand is ugly and error-prone. So derive
it automatically from the mask instead.

Macros cannot #define other macros, so we now declare enums instead.

This also adds macros for decoding the register definitions. These will
be used by later commits.
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230514170323.3408798-1-oswald.buddenhagen@gmx.deSigned-off-by: Takashi Iwai <tiwai@suse.de>