hw/isa/lpc_ich9: inject the SMI on the VCPU that is writing to APM_CNT

hw/isa/lpc_ich9: inject the SMI on the VCPU that is writing to APM_CNT

Commit 4d00636e97b7 ("ich9: Add the lpc chip", Nov 14 2012) added the
ich9_apm_ctrl_changed() ioport write callback function such that it would
inject the SMI, in response to a write to the APM_CNT register, on the
first CPU, invariably.

Since this register is used by guest code to trigger an SMI synchronously,
the interrupt should be injected on the VCPU that is performing the write.

apm_ioport_writeb() is the .write callback of the "apm_ops"
MemoryRegionOps [hw/isa/apm.c]; it is parametrized to call
ich9_apm_ctrl_changed() by ich9_lpc_init() [hw/isa/lpc_ich9.c], via
apm_init(). Therefore this change affects no other board.

ich9_generate_smi() is an unrelated function that is called by the TCO
watchdog; a watchdog is likely in its right to (asynchronously) inject
interrupts on the first CPU only.

This patch allows the combined edk2/OVMF SMM driver stack to work with
multiple VCPUs on TCG, using both qemu-system-i386 and qemu-system-x86_64.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>