regulator: of: Add regulator desc param to of_get_regulator_init_data()

The of_get_regulator_init_data() function is used to extract the regulator
init_data but information on how to extract certain data is defined in the
static regulator descriptor (e.g: how to map the hardware operating modes).

Add a const struct regulator_desc * parameter to the function signature so
the parsing logic could use the information in the struct regulator_desc.

of_get_regulator_init_data() relies on of_get_regulation_constraints() to
actually extract the init_data so it has to pass the struct regulator_desc
but that is modified on a later patch.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>