KVM: Implement NotifyLongSpinWait HYPER-V hypercall

Windows issues this hypercall after guest was spinning on a spinlock
for too many iterations.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Vadim Rozenfeld <vrozenfe@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 5ce6173..4c4937e 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -499,6 +499,7 @@
 #define KVM_CAP_PPC_SEGSTATE 43
 #define KVM_CAP_HYPERV 44
 #define KVM_CAP_HYPERV_VAPIC 45
+#define KVM_CAP_HYPERV_SPIN 46
 
 #ifdef KVM_CAP_IRQ_ROUTING