In runtime suspended state, we are not expecting IRQs and thus we can
safely mask them, not only for pwrreg_nopower variants but for all.

Obviously we then also need to make sure we restore the IRQ mask while
becoming runtime resumed.

Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>