HV: improve pass-thru device interrupt process

for each pass-thru device and its entry owned by one VM, so
change the pass-thru device's softirq lock & entry list into
per VM, so one VM's PT device interrupt process will not
interfere with other VMs; especially in case one user OS
"interrupt storm" happens, it will have little effect on
service OS.

Tracked-On: #866
Signed-off-by: Minggui Cao <minggui.cao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/include/arch/x86/guest/vm.h

@@ -167,6 +167,9 @@ struct vm {
 	struct vpci vpci;
 	uint8_t vrtc_offset;
 #endif
+
+	spinlock_t softirq_dev_lock;
+	struct list_head softirq_dev_entry_list;
 };
 
 #ifdef CONFIG_PARTITION_MODE