staging: lustre: ldlm: remove unneeded 'err' arg to ldlm_process_flock_lock()

This arg is used to return an error code, but the returned code is never
looked at.  So there is no point returning it.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>