lib/vsprintf: Hash printed address for netdev bits fallback

The handler for "%pN" falls back to printing the raw pointer value when
using a different format than the (sole supported) special format
"%pNF", potentially leaking sensitive information regarding the kernel
layout in memory.

Avoid this leak by printing the hashed address instead.
Note that there are no in-tree users of the fallback.

Fixes: ad67b74d

 ("printk: hash addresses printed with %p")
Link: http://lkml.kernel.org/r/20181011084249.4520-4-geert+renesas@glider.be
To: "Tobin C . Harding" <me@tobin.cc>
To: Andrew Morton <akpm@linux-foundation.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>