x86: Add pci_init_irq to x86_init

x86: Add pci_init_irq to x86_init

Moorestown wants to reuse pcibios_init_irq but needs to provide its
own implementation of pci_enable_irq. After we distangled the init we
can move the init_irq call to x86_init and remove the pci_enable_irq
!= NULL check in pcibios_init_irq. pci_enable_irq is compile time
initialized to pirq_enable_irq and the special cases which override it
(visws and acpi) set the x86_init function pointer to noop. That
allows MSRT to override pci_enable_irq and otherwise run
pcibios_init_irq unmodified.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80CFF@orsmsx508.amr.corp.intel.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>