regulator: core: Add error flags to sysfs attributes

If a regulator provides a get_error_flags() operation, its sysfs
attributes will now include an entry for each defined
REGULATOR_ERROR_* flag.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20220504065252.6955-3-zev@bewilderbeest.net
Signed-off-by: Mark Brown <broonie@kernel.org>