kernel: x86/hyperv: fix kexec crash due to VP assist page corruption

in cpuhpsetupstate a requisite condition of "hypervinitcpuhp 0" for the hyperv case will never be true, and then hvcpudie won't be called on all CPUs and the VP assist page will not be reset. This leads to corruption of the previous VP assist page and ultimately panic if the kexec kernel is using...