staging:lustre: remove obsolete comment in libcfs_ioctl.h

The libcfs_ioctl.h header has a comment about a snapshot ioctl
which has been removed for years. Lets remove the comment to
avoid confusion. Broken out of patch 17492.

Signed-off-by: Parinay Kondekar <parinay.kondekar@seagate.com>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5844
Reviewed-on: http://review.whamcloud.com/17492


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>