AMD IOMMU: fix fullflush comparison length

Impact: fix comparison length for 'fullflush'
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/kernel/amd_iommu_init.c

@@ -1215,7 +1215,7 @@ static int __init parse_amd_iommu_options(char *str)
 			amd_iommu_isolate = 1;
 		if (strncmp(str, "share", 5) == 0)
 			amd_iommu_isolate = 0;
-		if (strncmp(str, "fullflush", 11) == 0)
+		if (strncmp(str, "fullflush", 9) == 0)
 			amd_iommu_unmap_flush = true;
 	}