ahci: clean up PORT_IRQ_BAD_PMP enabling

Now that we have pp->intr_mask, move PORT_IRQ_BAD_PMP enabling to
ahci_pmp_attach/detach() where it belongs.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>