mfd: sec-core: Drop non-existing forward declarations

mfd: sec-core: Drop non-existing forward declarations

sec_irq_resume() was removed in commit 6445b84abf91 ("mfd: Add s2mps11
irq driver") and sec_irq_exit() in commit 3dc6f4aaafbe ("mfd: sec: Use
devm_mfd_add_devices and devm_regmap_add_irq_chip") while the
prototypes were left. They should be removed.

Do so.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250409-s2mpg10-v4-4-d66d5f39b6bf@linaro.org
Signed-off-by: Lee Jones <lee@kernel.org>