xen-kernel -- Information leak through XEN_DOMCTL_gettscinfo

The Xen Project reports:

The handler for XEN_DOMCTL_gettscinfo failed to initialize a
padding field subsequently copied to guest memory.
A similar leak existed in XEN_SYSCTL_getdomaininfolist, which is
being addressed here regardless of that operation being declared
unsafe for disaggregation by XSA-77.
Malicious or buggy stub domain kernels or tool stacks otherwise
living outside of Domain0 may be able to read sensitive data
relating to the hypervisor or other guests not under the control of
that domain.