mfd: Constify reg_sequence and regmap_irq

Static 'struct reg_sequence' array, 'struct regmap_irq_sub_irq_map' and
'struct regmap_irq_chip ' are not modified so can be changed to const
for more safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20250528194416.567127-2-krzysztof.kozlowski@linaro.org


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