x86, irq: Simplify the way to handle ISA IRQ

On startup, setup_IO_APIC_irqs() will program all IOAPIC pins for ISA
IRQs. Later when mp_map_pin_to_irq() is called, it just returns ISA IRQ
number without programming corresponding IOAPIC pin.

This patch consolidates the way to program IOAPIC pins for both ISA and
non-ISA IRQs into mp_map_pin_to_irq() as below:
1) For ISA IRQs, mp_irqs array is used to map IOAPIC pin to IRQ and
   mp_irqdomain_map() is used to actually program the pin.
2) For non-ISA IRQs, irqdomain is used to map IOAPIC pin to IRQ, and
   mp_irqdomain_map() is also used to actually program the pin.

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>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Link: http://lkml.kernel.org/r/1402302011-23642-36-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/acpi/boot.c

@@ -101,17 +101,6 @@ static u32 isa_irq_to_gsi[NR_IRQS_LEGACY] __read_mostly = {
 
 #define	ACPI_INVALID_GSI		INT_MIN
 
-static int map_gsi_to_irq(unsigned int gsi, unsigned int flags)
-{
-	int i;
-
-	for (i = 0; i < nr_legacy_irqs(); i++)
-		if (isa_irq_to_gsi[i] == gsi)
-			return i;
-
-	return mp_map_gsi_to_irq(gsi, flags);
-}
-
 /*
  * This is just a simple wrapper around early_ioremap(),
  * with sanity checks for phys == 0 and size == 0.
@@ -422,7 +411,7 @@ static int mp_register_gsi(struct device *dev, u32 gsi, int trigger,
 		return -1;
 	}
 
-	irq = map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC);
+	irq = mp_map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC);
 	if (irq < 0)
 		return irq;
 
@@ -603,7 +592,7 @@ void __init acpi_pic_sci_set_trigger(unsigned int irq, u16 trigger)
 
 int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
 {
-	int irq = map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
+	int irq = mp_map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
 
 	if (irq >= 0) {
 		*irqp = irq;