mfd: ab8500-core: APE Interrupts are not cleared

There are missing register descriptions from the AB8505 user manual
and these need to be masked so that the APEINT line can toggle.
This patch also affects the behaviour of AB9540.

Signed-off-by: Marcus Cooper <marcus.xm.cooper@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Maxime COQUELIN <maxime.coquelin@stericsson.com>
Reviewed-by: Alexandre TORGUE <alexandre.torgue@stericsson.com>
Reviewed-by: Mattias WALLIN <mattias.wallin@stericsson.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>