HV: Install a NMI handler in acrn IDT

This patch installs a NMI handler in acrn IDT to handle
NMIs out of dispatch_exception.

Tracked-On: #3886
Acked-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Kaige Fu <kaige.fu@intel.com>

hypervisor/include/arch/x86/irq.h

@@ -302,6 +302,15 @@ uint32_t irq_to_vector(uint32_t irq);
  */
 void dispatch_interrupt(const struct intr_excp_ctx *ctx);
 
+/**
+ * @brief Handle NMI
+ *
+ * To handle an NMI
+ *
+ * @param ctx Pointer to interrupt exception context
+ */
+void handle_nmi(__unused struct intr_excp_ctx *ctx);
+
 /**
  * @brief Initialize interrupt
  *