acpi/doc: add missing param value

Add missing parameter value to list of available values
for acpi=<value>.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-parameters.txt

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b182626..319785b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -134,7 +134,7 @@
 
 	acpi=		[HW,ACPI,X86-64,i386]
 			Advanced Configuration and Power Interface
-			Format: { force | off | ht | strict | noirq }
+			Format: { force | off | ht | strict | noirq | rsdt }
 			force -- enable ACPI if default was off
 			off -- disable ACPI if default was on
 			noirq -- do not use ACPI for IRQ routing