Fix to return negative error code -ENOMEM from create_afu error handling
case instead of 0, as done elsewhere in this function.

Link: https://lore.kernel.org/r/20200428141855.88704-1-weiyongjun1@huawei.comAcked-by: Matthew R. Ochs <mrochs@linux.ibm.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>