usb: acpi: Prevent null pointer dereference in usb_acpi_add_usb4_devlink()

In the Linux kernel, the following vulnerability has been resolved: usb: acpi: Prevent null pointer dereference in usb_acpi_add_usb4_devlink() As demonstrated by the fix for update_port_device_state, commit 12783c0b9e2c ("usb: core: Prevent null pointer dereference in update_port_device_state"), usb_hub_to_struct_hub() can return NULL in certain scenarios, such as during hub driver unbind or teardown race conditions, even if the underlying usb_device structure exists. Plus, all other places that call usb_hub_to_struct_hub() in the same file do check for NULL return values. If usb_hub_to_struct_hub() returns NULL, the subsequent access to hub->ports[udev->portnum - 1] will cause a null pointer dereference.