Move all kmemleak calls into hook functions, and make it so
that all hooks (both inside and outside of #ifdef CONFIG_SLUB_DEBUG)
call the appropriate kmemleak routines.  This allows for kmemleak
to be configured independently of slub debug features.

It also fixes a bug where kmemleak was only partially enabled in some
configurations.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NRoman Bobniev <Roman.Bobniev@sonymobile.com>
Signed-off-by: NTim Bird <tim.bird@sonymobile.com>
Signed-off-by: NPekka Enberg <penberg@iki.fi>