mm/slab.c: do not hash pointers when debugging slab

If CONFIG_DEBUG_SLAB/CONFIG_DEBUG_SLAB_LEAK are enabled, the slab code
prints extra debug information when e.g.  corruption is detected.  This
includes pointers, which are not very useful when hashed.

Fix this by using %px to print unhashed pointers instead where it makes
sense, and by removing the printing of a last user pointer referring to
code.

[geert+renesas@glider.be: v2]
  Link: http://lkml.kernel.org/r/1513179267-2509-1-git-send-email-geert+renesas@glider.be
Link: http://lkml.kernel.org/r/1512641861-5113-1-git-send-email-geert+renesas@glider.be
Fixes: ad67b74d

 ("printk: hash addresses printed with %p")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Kees Cook <keescoo...