In physical destination mode, the destination processor is specified by its
local APIC ID. When a CPU switch xAPIC Mode to x2APIC Mode or vice versa,
the local APIC ID is not changed. So a vcpu in x2APIC Mode could use physical
Destination Mode to send an IPI to another vcpu in xAPIC Mode by writing ICR.
This patch adds support for a vCPU A could write ICR to send IPI to another
vCPU B which is in different APIC mode.
Tracked-On: #5923
Signed-off-by: Li Fei1 <fei1.li@intel.com>