virt: drop an unused assignment

As `v` gets overwritten by the following detect_vm_cpuid() call.

Resolves: CID#1509247

src/basic/virt.c

@@ -492,8 +492,6 @@ Virtualization detect_vm(void) {
                         return xen_dom0;
                 if (xen_dom0 == 0)
                         goto finish;
-
-                v = VIRTUALIZATION_NONE;
         } else if (v != VIRTUALIZATION_NONE)
                 assert_not_reached();