vhost-vdpa: fix msi irq request err

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I86ITO



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When we call vhost_vdpa_reset, vdpa device pci driver may request irq,
at this time, wo have not init msi iova for device, may cause an error,
call vhost_vdpa_alloc_domain first to avoid this scene.

Signed-off-by: jiangdongxu <jiangdongxu1@huawei.com>