staging: brcm80211: use '%pM' format to print MAC address

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Nohee Ko <noheek@broadcom.com>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>