regulator: Use container_of_const() when all types are const

regulator: Use container_of_const() when all types are const

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.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20251126-container-of-const-regulator-v1-1-eeec378144d4@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>