regmap: kunit: Constify regmap_range_cfg array

Static 'struct regmap_range_cfg' array is not modified so can be changed
to const for more safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250528194501.567366-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>