net/virtio-user: fix device type check

net/virtio-user: fix device type check

Segfault happens when using virtio-user after commit 7f0a669e7b04
("ethdev: add allocation helper for virtual drivers").

It's due to we use ethdev->device to recognize physical devices,
but after above commit, this field is also filled for virtual
devices. Then we obtain the wrong pci_dev pointer and accessing
its field when copying pci info results in segfault.

To fix it, we use hw->virtio_user_dev to differentiate physical
devices from virtual devices.

Fixes: 6a7c0dfcdf40 ("net/virtio: do not depend on PCI device of ethdev")

Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>