iio: add addac subdirectory

stable inclusion
from stable-v5.10.192
commit c5e580831b2dd4eb42b3f1baccec7ea3e4fb6077
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I933RF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c5e580831b2dd4eb42b3f1baccec7ea3e4fb6077



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[ Upstream commit b62e2e17 ]

For IIO devices that expose both ADC and DAC functionality.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Link: https://lore.kernel.org/r/20211205114045.173612-2-cosmin.tanislav@analog.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Stable-dep-of: 4f9b80ae ("iio: addac: stx104: Fix race condition when converting analog-to-digital")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>