Documentation: Add CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF case

This patch add a case with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/kmemleak.txt

@@ -62,6 +62,10 @@ Memory may be allocated or freed before kmemleak is initialised and
 these actions are stored in an early log buffer. The size of this buffer
 is configured via the CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE option.
 
+If CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF are enabled, the kmemleak is
+disabled by default. Passing "kmemleak=on" on the kernel command
+line enables the function. 
+
 Basic Algorithm
 ---------------