Legacy PIC (8259) cannot be supported for TDX guests since TDX module
doesn't allow directly interrupt injection.  Using posted interrupts
for the PIC is not a viable option as the guest BIOS/kernel will not
do EOI for PIC IRQs, i.e. will leave the vIRR bit set.

Make PIC the property of common x86 machine type. Hence all x86
machines, including microvm, can disable it.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20220310122811.807794-3-xiaoyao.li@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>