BACKPORT: lib/vsprintf: Hash legacy clock addresses

On platforms using the Common Clock Framework, "%pC" prints the clock's
name. On legacy platforms, it prints the unhashed clock's address,
potentially leaking sensitive information regarding the kernel layout in
memory.

Avoid this leak by printing the hashed address instead.  To distinguish
between clocks, a 32-bit unique identifier is as good as an actual
pointer value.

Bug: 254441685
Fixes: ad67b74d ("printk: hash addresses printed with %p")
Link: http://lkml.kernel.org/r/20181011084249.4520-3-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>
(cherry picked from commit ec12bc2909f9759747ab5ad3709472353c43a750)
[Lee: Fixed a trivial conflict pertaining to original diff]
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I8286a3b34ebd66ddef861dd969c68283ef569cf5