pm8001: Fix invalid return when request_irq() failed

When a call to request_irq() failed pm8001_setup_msix()
still returns the success. This udate fixes the described
misbehaviour.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Acked-by: Jack Wang <xjtuwjp@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>