ACPI / Documentation: add copy_dsdt to ACPI format options

commit aa2110cb (ACPI: add boot option acpi=copy_dsdt to fix corrupt
DSDT) added copy_dsdt as an ACPI boot option, but did not add it to ACPI
format options in Documentation/kernel-parameters.txt.  Fix that.
Signed-off-by: Rami Rosen <ramirose@gmail.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/kernel-parameters.txt

@@ -167,7 +167,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	acpi=		[HW,ACPI,X86,ARM64]
 			Advanced Configuration and Power Interface
-			Format: { force | off | strict | noirq | rsdt }
+			Format: { force | off | strict | noirq | rsdt |
+				  copy_dsdt }
 			force -- enable ACPI if default was off
 			off -- disable ACPI if default was on
 			noirq -- do not use ACPI for IRQ routing