doc/kmemcheck: add kmemcheck to kernel-parameters

Add "kmemcheck=xx" to Documentation/kernel-parameters.txt.
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Cc: Vegard Nossum <vegardno@ifi.uio.no>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-parameters.txt

@@ -1445,6 +1445,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Valid arguments: on, off
 			Default: on
 
+	kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
+			Valid arguments: 0, 1, 2
+			kmemcheck=0 (disabled)
+			kmemcheck=1 (enabled)
+			kmemcheck=2 (one-shot mode)
+			Default: 2 (one-shot mode)
+
 	kstack=N	[X86] Print N words from the kernel stack
 			in oops dumps.