ACPI: Add kernel-parameters hint that acpi=off doesn't work on IA64.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/kernel-parameters.txt

@@ -125,7 +125,8 @@ and is between 256 and 4096 characters. It is defined in the file
 			See header of drivers/scsi/53c7xx.c.
 			See also Documentation/scsi/ncr53c7xx.txt.
 
-	acpi=		[HW,ACPI] Advanced Configuration and Power Interface
+	acpi=		[HW,ACPI,X86-64,i386]
+			Advanced Configuration and Power Interface
 			Format: { force | off | ht | strict | noirq }
 			force -- enable ACPI if default was off
 			off -- disable ACPI if default was on