vsprintf: add %pMR for Bluetooth MAC address

Bluetooth uses mostly LE byte order which is reversed for visual
interpretation.  Currently in Bluetooth in use unsafe batostr function.

This is a slightly modified version of Joe's patch (sent Sat, Dec 4,
2010).

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>