iommu/amd: Fix typo in kernel-parameters.txt

Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

Documentation/kernel-parameters.txt

@@ -320,7 +320,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			on: enable for both 32- and 64-bit processes
 			off: disable for both 32- and 64-bit processes
 
-	amd_iommu=	[HW,X86-84]
+	amd_iommu=	[HW,X86-64]
 			Pass parameters to the AMD IOMMU driver in the system.
 			Possible values are:
 			fullflush - enable flushing of IO/TLB entries when