regulator: Use container_of_const() when all types are

regulator: Use container_of_const() when all types are

Merge series from Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>:

Use container_of_const(), which is preferred over container_of(), when
the argument 'ptr' and returned pointer are already const, for better
code safety and readability.

Some drivers already have const everywhere, so container_of_const can be
directly used. In few other drivers, the final pointer can be constified
that way.