staging: lustre: Dynamic LNet Configuration (DLC) IOCTL changes

This is the fourth patch of a set of patches that enables DLC.

This patch changes the IOCTL infrastructure in preparation of
adding extra IOCTL communication between user and kernel space.
The changes include:
- adding a common header to be passed to ioctl infra functions
  instead of passing an exact structure.  This header is meant
  to be included in all structures to be passed through that
  interface.  The IOCTL handler casts this header to a particular
  type that it expects
- All sanity testing on the past in structure is performed in the
  generic ioctl infrastructure code.
- All ioctl handlers changed to take the header instead of a
  particular structure type

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2456
Reviewed-on: http://review.whamcloud.com/8021


Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.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>