staging/lustre: move /proc/fs/lustre/devices to debugfs

the devices file prints out status information about all
obd devices in the system in human readable form.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>