staging: lustre: make ldebugfs_add_vars a void function

staging: lustre: make ldebugfs_add_vars a void function

The call to ldebugfs_add_vars() can not really fail, so have it just
return nothing, which allows us to clean up a lot of unused error
handling code.

Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: James Simmons <jsimmons@infradead.org>
Cc: NeilBrown <neilb@suse.com>
Cc: Roman Storozhenko <romeusmeister@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Quentin Bouget <quentin.bouget@cea.fr>
Cc: Aastha Gupta <aastha.gupta4104@gmail.com>
Cc: Ben Evans <bevans@cray.com>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Arushi Singhal <arushisinghal19971997@gmail.com>
Cc: Frank Zago <fzago@cray.com>
Cc: Patrick Farrell <paf@cray.com>
Cc: Simo Koskinen <koskisoft@gmail.com>
Cc: Andriy Skulysh <andriy.skulysh@seagate.com>
Cc: "John L. Hammond" <john.hammond@intel.com>
Cc: Mathias Rav <mathiasrav@gmail.com>
Cc: Dafna Hirschfeld <dafna3@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>