This patch fixes the problem that "irq XX: nobody cared" kernel oops
is reported when pciehp is once rmmoded and insmoded again. The cause
of this problem is pciehp driver calls pci_disable_msi() at controller
release time, even though it must be done by PCI Express Port Bus
driver. This patch removes unnecessary pci_disable_msi() call from
pciehp driver.