qcacmn: Add API to print scheduler history

The scheduler maintains a history of the recent messages
in the scheduler that were queued, started or completed execution.

This information can be reviewed while debugging issues
if the scheduler is taking longer to process any message.

The new API will print the scheduler history on request.

Change-Id: I2ed7989296f6891cfd9779e7b96383253d680f51
CRs-Fixed: 2599281

scheduler/inc/scheduler_api.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2019 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2014-2020 The Linux Foundation. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -92,6 +92,15 @@ struct scheduler_msg {
 #endif /* WLAN_SCHED_HISTORY_SIZE */
 };
 
+/**
+ * sched_history_print() - print scheduler history
+ *
+ * This API prints the scheduler history.
+ *
+ * Return: None
+ */
+void sched_history_print(void);
+
 typedef QDF_STATUS (*scheduler_msg_process_fn_t) (struct scheduler_msg  *msg);
 typedef void (*hdd_suspend_callback)(void);