[PATCH] Altix: more ACPI PRT support

The SN Altix platform does not conform to the IOSAPIC IRQ routing model.
Add code in acpi_unregister_gsi() to check if (acpi_irq_model ==
ACPI_IRQ_MODEL_PLATFORM) and return.

Due to an oversight, this code was not added previously when
similar code was added to acpi_register_gsi().

http://marc.theaimsgroup.com/?l=linux-acpi&m=116680983430121&w=2

Signed-off-by: John Keller <jpk@sgi.com>
Acked-by: Len Brown <lenb@kernel.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/ia64/kernel/acpi.c

@@ -609,6 +609,9 @@ EXPORT_SYMBOL(acpi_register_gsi);
 
 void acpi_unregister_gsi(u32 gsi)
 {
+	if (acpi_irq_model == ACPI_IRQ_MODEL_PLATFORM)
+		return;
+
 	iosapic_unregister_intr(gsi);
 }