KVM: VMX: Move emulation_required to struct vcpu_vt

Move emulation_required from struct vcpu_vmx to struct vcpu_vt so that
vmx_handle_exit_irqoff() can be reused by TDX code.

No functional change intended.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Message-ID: <20250222014757.897978-14-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>