KVM: x86: remove dead initialization

hv_vcpu is initialized again a dozen lines below, and at this
point vcpu->arch.hyperv is not valid.  Remove the initializer.

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>