mfd: twl6030-irq: Add error check when IRQs are masked initially

Add a missed check for errors when TWL IRQs are masked
initially on probe and report an error in case of failure.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>