x86, acpi, irq: Kill static function irq_to_gsi()

Static function irq_to_gsi() is only called by acpi_isa_irq_to_gsi(),
so kill function irq_to_gsi() and simplify acpi_isa_irq_to_gsi().
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/1402302011-23642-7-git-send-email-jiang.liu@linux.intel.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/acpi/boot.c

@@ -120,22 +120,6 @@ static unsigned int gsi_to_irq(unsigned int gsi)
 	return irq;
 }
 
-static u32 irq_to_gsi(int irq)
-{
-	unsigned int gsi;
-
-	if (irq < NR_IRQS_LEGACY)
-		gsi = isa_irq_to_gsi[irq];
-	else if (irq < gsi_top)
-		gsi = irq;
-	else if (irq < (gsi_top + NR_IRQS_LEGACY))
-		gsi = irq - gsi_top;
-	else
-		gsi = 0xffffffff;
-
-	return gsi;
-}
-
 /*
  * This is just a simple wrapper around early_ioremap(),
  * with sanity checks for phys == 0 and size == 0.
@@ -640,10 +624,12 @@ EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
 
 int acpi_isa_irq_to_gsi(unsigned isa_irq, u32 *gsi)
 {
-	if (isa_irq >= 16)
-		return -1;
-	*gsi = irq_to_gsi(isa_irq);
-	return 0;
+	if (isa_irq < NR_IRQS_LEGACY) {
+		*gsi = isa_irq_to_gsi[isa_irq];
+		return 0;
+	}
+
+	return -1;
 }
 
 static int acpi_register_gsi_pic(struct device *dev, u32 gsi,