x86, irq: Introduce two helper functions to support irqdomain map operation

Currently there are multiple entries to program IOAPIC pins, such as
io_apic_setup_irq_pin_once(), io_apic_set_pci_routing() and
setup_IO_APIC_irq_extra() etc.

This patch introduces two functions to help consolidate the code to
program IOAPIC pins. Function mp_set_pin_attr() is used to optionally
set trigger, polarity and NUMA node property for an IOAPIC pin.
If mp_set_pin_attr() is not invoked for a pin, the default configuration
from BIOS will be used.

Function mp_irqdomain_map() is an common implementation of irqdomain map()
operation. It figures out attribures for pin and then actually programs
the IOAPIC pin. We hope this will be the only entrance for programming
IOAPIC pin.

And the flow will:
1) caller such as xxx_pci_irq_enable figures out pin attributes.
2) Invoke mp_set_pin_attr() to set attributes for a pin. If the pin has
   already bin programmed,  mp_set_pin_attr() will aslo detects attribute
   confictions.
3) Invoke mp_map_pin_to_irq()
3.1) If IRQ has already been assigned, return irq_find_mapping()
3.2) Else irq_create_mapping()
		->irq_domain_associate()
			->mp_irqdomain_map()
				->io_apic_setup_irq_pin()

So every pin will only programmed once by mp_irqdomain_map(), so we
could kill io_apic_setup_irq_pin_once(), io_apic_set_pci_routing() and
setup_IO_APIC_irq_extra() etc.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1402302011-23642-30-git-send-email-jiang.liu@linux.intel.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>