regulator: core: remove machine init callback from config

The machine specific regulator_init() appears to be unused.
It does not allow a lot of interaction with the regulator framework,
since nothing from the framework is passed along (desc, config,
etc ...)

Machine specific init may also be done with the added init_cb() in
the regulator description, so remove regulator_init().

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://patch.msgid.link/20241008-regulator-ignored-data-v2-3-d1251e0ee507@baylibre.com


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