PCI/MSI: Free legacy IRQ when enabling MSI/MSI-X

Once MSI/MSI-X is enabled by the device driver, a PCI device won't use
legacy IRQs again until MSI/MSI-X is disabled.

Call pcibios_free_irq() when enabling MSI/MSI-X and pcibios_alloc_irq()
when disabling MSI/MSI-X.  This allows arch code to manage resources
associated with the legacy IRQ.

[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>