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.

diff --cc MAINTAINERS
Simple merge

diff --cc drivers/regulator/Kconfig
Simple merge

diff --cc drivers/regulator/Makefile
Simple merge

diff --cc drivers/regulator/bd718x7-regulator.c
Simple merge

diff --cc drivers/regulator/pca9450-regulator.c
Simple merge

diff --cc drivers/regulator/pf9453-regulator.c
Simple merge