PCI: Add helpers to manage pci_dev->irq and pci_dev->irq_managed

Add pci_has_managed_irq(), pci_set_managed_irq(), and
pci_reset_managed_irq() to simplify code.  No functional change.

[bhelgaas: changelog]
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>