LU-6142 lustre: remove ldebugfs_register_stats() wrapper

LU-6142 lustre: remove ldebugfs_register_stats() wrapper

It was just calling debugfs_create_file() so unwind things and just
call the real function instead.  This ends up saving a number of lines
as there was never any error handling happening anyway, so that all
can be removed as well.

Test-Parameters: trivial
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I7e30139cc8e810ab4bc49ae9c298e6199c3f2942
Reviewed-on: https://review.whamcloud.com/37746
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>