vfio/pci: Fix wrong return value when get iommu attribute DOMAIN_ATTR_NESTING

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I46K8O


CVE: NA

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Some vendor IOMMU drivers doesn't implement their own domain_get_attr
callback or the processing of DOMAIN_ATTR_NESTING. Then
iommu_domain_get_attr may return an error. But it shouldn't affect the
result of vfio_pci_enable. We print a log to indicate the error and
return 0.

Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Reviewed-by: Xinle Guo <guoxinle1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>