vdpa: fix use-after-free on vp_vdpa_remove

In the Linux kernel, the following vulnerability has been resolved:

vdpa: fix use-after-free on vp_vdpa_remove

When vp_vdpa driver is unbind, vp_vdpa is freed in vdpa_unregister_device

and then vp_vdpa->mdev.pci_dev is dereferenced in vp_modern_remove,

triggering use-after-free.

Call Trace of unbinding driver free vp_vdpa :

do_syscall_64

vfs_write

kernfs_fop_write_iter

device_release_driver_internal

pci_device_remove

vp_vdpa_remove

vdpa_unregister_device

kobject_release

device_release

kfree

Call Trace of dereference vp_vdpa->mdev.pci_dev:

vp_modern_remove

pci_release_selected_regions

pci_release_region

pci_resource_len

pci_resource_end

(dev)->resource[(bar)].end