xen: enable Virtual-interrupt delivery

xen: enable Virtual-interrupt delivery

Virtual interrupt delivery avoids Xen to inject vAPIC interrupts
manually, which is fully taken care of by the hardware. This needs
some special awareness into existing interrupr injection path:
For pending interrupt from vLAPIC, instead of direct injection, we may
need update architecture specific indicators before resuming to guest.
Before returning to guest, RVI should be updated if any pending IRRs
EOI exit bitmap controls whether an EOI write should cause VM-Exit. If
set, a trap-like induced EOI VM-Exit is triggered. The approach here
is to manipulate EOI exit bitmap based on value of TMR. Level
triggered irq requires a hook in vLAPIC EOI write, so that vIOAPIC EOI
is triggered and emulated

Signed-off-by: Gang Wei <gang.wei@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Signed-off-by: Jiongxi Li <jiongxi.li@intel.com>
Committed-by: Keir Fraser <keir@xen.org>