staging: lustre: ldlm: check all errors during ldlm_debugfs_setup()

staging: lustre: ldlm: check all errors during ldlm_debugfs_setup()

Fix ignoring errors from ldebugfs_add_vars() function.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3885
Reviewed-on: http://review.whamcloud.com/8115
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>