mm/sl[ao]b: always track caller in kmalloc_(node_)track_caller()

Now, we track caller if tracing or slab debugging is enabled.  If they are
disabled, we could save one argument passing overhead by calling
__kmalloc(_node)().  But, I think that it would be marginal.  Furthermore,
default slab allocator, SLUB, doesn't use this technique so I think that
it's okay to change this situation.

After this change, we can turn on/off CONFIG_DEBUG_SLAB without full
kernel build and remove some complicated '#if' defintion.  It looks more
benefitial to me.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>