mfd: bd9576: Add IRQ support

mfd: bd9576: Add IRQ support

BD9573 and BD9576 support set of "protection" interrupts for "fatal"
issues. Those lead to SOC reset as PMIC shuts the power outputs. Thus
there is no relevant IRQ handling for them.

Few "detection" interrupts were added to the BD9576 with the idea that
SOC could take some recovery-action before error gets unrecoverable.

Unfortunately the BD9576 interrupt logic was not re-evaluated. IRQs
are not designed to be properly acknowleged - and IRQ line is kept
active for whole duration of error condition (in comparison to
informing only about state change).

For above reason, do not consider missing IRQ as error.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>