ALSA: hda/ca0132 - Add 8051 exram helper functions.

Add functions for both reading and writing to the 8051's exram. Also,
add a little bit of documentation on how the addresses are segmented.

Signed-off-by: Connor McAdams <conmanx360@gmail.com>
Link: https://lore.kernel.org/r/20201210160658.461739-4-conmanx360@gmail.com


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