mfd: wcd9xxx: Let system suspend and lock it later

When wcd9xxx codec receives IRQ, codec driver acquires suspend lock to
prevent system from entering suspend and waits until either system is
already awake or is awoken.
However if power management interface is already in the middle of calling
suspend chains, codec cannot lock suspend.
For this case, let the power management interface to proceed suspend and
make codec driver not to handle IRQ for now so unhandled IRQ would raise
shortly again.

Change-Id: Ia06394a890fe0c5fbde65d482d584346d167132a
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>