regulator: expose regulator_find_closest_bigger

Expose and document the table lookup logic used by
regulator_set_ramp_delay_regmap, so that it can be
reused for devices that cannot be configured via
regulator_set_ramp_delay_regmap.

Tested-by: Diederik de Haas <didi.debian@cknow.org> # Rock64, Quartz64 Model A + B
Tested-by: Vincent Legoll <vincent.legoll@gmail.com> # Pine64 QuartzPro64
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230504173618.142075-11-sebastian.reichel@collabora.com


Signed-off-by: Mark Brown <broonie@kernel.org>