regulator: Implement uv_survival_time for handling under-voltage events

regulator: Implement uv_survival_time for handling under-voltage events

Add 'uv_survival_time' field to regulation_constraints for specifying
survival time post critical under-voltage event. Update the regulator
notifier call chain and Device Tree property parsing to use this new
field, allowing a configurable timeout before emergency shutdown.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20231026144824.4065145-6-o.rempel@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>