regulator: Add support for power budget

Introduce power budget management for the regulator device. Enable tracking
of available power capacity by providing helpers to request and release
power budget allocations.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20250115-feature_regulator_pw_budget-v2-1-0a44b949e6bc@bootlin.com


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