DM: register pm ops to monitor

Then, acrnctl could send command to monitor module of DM and call
functions defined in pm ops. One example is: acrnctl resume UOS
after UOS enter S3.

Also add general pm.c and move pm related function to this file.

Signed-off-by: Yan Like <like.yan@intel.com>
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

devicemodel/include/pm.h

@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) <2018> Intel Corporation
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef	_DM_INCLUDE_PM_
+#define	_DM_INCLUDE_PM_
+
+int wait_for_resume(struct vmctx *ctx);
+int vm_resume(struct vmctx *ctx);
+int vm_monitor_resume(void *arg);
+int vm_monitor_query(void *arg);
+
+#endif