mfd: palmas: Constify strings with regulator names

The names of regulators are static const strings, so pointers can be made
as pointers to const for code safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240909134941.121847-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>