staging: lustre: llite: check ret of ll_prep_md_op_data in ll_dir_filler

staging: lustre: llite: check ret of ll_prep_md_op_data in ll_dir_filler

ll_dir_filler() now checks the returned pointer from
ll_prep_md_op_data() using IS_ERR()

Signed-off-by: Swapnil Pimpale <[email protected]>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4082
Reviewed-on: http://review.whamcloud.com/8073
Reviewed-by: Dmitry Eremin <[email protected]>
Reviewed-by: John L. Hammond <[email protected]>
Reviewed-by: Oleg Drokin <[email protected]>
Signed-off-by: James Simmons <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>