regulator: core: add callback to perform runtime init

Provide an initialisation callback to handle runtime parameters.
The idea is similar to the regulator_init() callback, but it provides
regulator specific structures, instead of just the driver specific data.

As an example, this allows the driver to amend the regulator constraints
based on runtime parameters if necessary.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://patch.msgid.link/20241008-regulator-ignored-data-v2-2-d1251e0ee507@baylibre.com


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