kmemleak: Introduce a default off mode for kmemleak
Introduce a new DEBUG_KMEMLEAK_DEFAULT_OFF config parameter that allows
kmemleak to be disabled by default, but enabled on the command line
via: kmemleak=on. Although a reboot is required to turn it on, its still
useful to not require a re-compile.
Signed-off-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>