CVE-2025-40160 xen/events: Return -EEXIST for bound VIRQs

In the Linux kernel, the following vulnerability has been resolved: xen/events: Return -EEXIST for bound VIRQs Change findvirq to return -EEXIST when a VIRQ is bound to a different CPU than the one passed in. With that, remove the BUGON from bindvirqtoirq to propogate the error upwards. Some VIRQ...