staging: lustre: remove ldebugfs_add_simple() wrapper

It was only being called in one place, and is an unneeded wrapper
function around debugfs_create_file() so just call the real debugfs
function instead.  This ends up cleaning up some unneeded error handling
logic that was never needed as well.

Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: James Simmons <jsimmons@infradead.org>
Cc: Quentin Bouget <quentin.bouget@cea.fr>
Cc: Ben Evans <bevans@cray.com>
Cc: NeilBrown <neilb@suse.com>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Arushi Singhal <arushisinghal19971997@gmail.com>
Cc: Dafna Hirschfeld <dafna3@gmail.com>
Cc: Mathias Rav <mathiasrav@gmail.com>
Cc: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
Cc: lustre-devel@lists.lustre.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>