staging: lustre: headers: Create single .h for lu_seq_range

Put lu_seq_range related functions into a single .h.
Include directly from files which use it, and remove
definitions from lustre_idl.h.

Signed-off-by: Ben Evans <bevans@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6401
Reviewed-on: http://review.whamcloud.com/15952


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>