KVM: x86: Disable posted interrupts for non-standard IRQs delivery modes

We can easily route hardware interrupts directly into VM context when
they target the "Fixed" or "LowPriority" delivery modes.

However, on modes such as "SMI" or "Init", we need to go via KVM code
to actually put the vCPU into a different mode of operation, so we can
not post the interrupt

Add code in the VMX and SVM PI logic to explicitly refuse to establish
posted mappings for advanced IRQ deliver modes. This reflects the logic
in __apic_accept_irq() which also only ever passes Fixed and LowPriority
interrupts as posted interrupts into the guest.

This fixes a bug I have with code which configures real hardware to
inject virtual SMIs into my guest.

Signed-off-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Wanpeng Li <wanpengli@tencent.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>