iio: adc: stx104: Implement and utilize register structures

stable inclusion
from stable-v5.10.192
commit f6576d4851facdfdfbca4280994c17e4cc93e2db
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=f6576d4851facdfdfbca4280994c17e4cc93e2db



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[ Upstream commit 6cfd14c5 ]

Reduce magic numbers and improve code readability by implementing and
utilizing named register data structures.

Tested-by: Fred Eckert <Frede@cmslaser.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/8cb91d5b53e57b066120e42ea07000d6c7ef5543.1657213745.git.william.gray@linaro.org


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>