There are two problems with using regcache in this module.

The amplifier has 3 addressing levels (BOOK, PAGE, REG). The firmware
contains blocks that must be written to BOOK 0x8C. The regcache doesn't
know anything about BOOK, so regcache_sync writes invalid values to the
actual BOOK.

The module handles 2 or more separate amplifiers. The amplifiers have
different register values, and the module uses only one regmap/regcache
for all the amplifiers. The regcache_sync only writes the last amplifier
used.

The module successfully restores all the written register values (RC
profile, program, configuration, calibration) without regcache.

Remove regcache functions and set regmap cache_type to REGCACHE_NONE.

Link: https://lore.kernel.org/r/21a183b5a08cb23b193af78d4b1114cc59419272.1701906455.git.soyer@irl.hu/

Fixes: 5be27f1e ("ALSA: hda/tas2781: Add tas2781 HDA driver")
Acked-by: Mark Brown <broonie@kernel.org>
CC: stable@vger.kernel.org
Signed-off-by: Gergo Koteles <soyer@irl.hu>
Link: https://lore.kernel.org/r/491aeed0e2eecc3b704ec856f815db21bad3ba0e.1703202126.git.soyer@irl.huSigned-off-by: Takashi Iwai <tiwai@suse.de>