mfd: max8997: Disable interrupt handling for suspend/resume cycle

Disable IRQs during suspend/resume cycle to ensure handling of wakeup
interrupts (i.e. RTC wake alarm) after max8997_resume(). This way it can
be properly handled when I2C bus is finally available. This pattern is
also used in other MAX PMIC MFD drivers.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>