Added common termination primitive for the worker tasks

Both of the worker tasks must signal their result through the message queue,
and then kill themselves - common work refactored in.

EDISOFT/src/common.c

+#include <printk.h>
+#include "system.h"
+
+void die(int task_no, unsigned exitCode)
+{
+    rtems_status_code status = RTEMS_SUCCESSFUL;
+
+    exitCode = exitCode << 31;
+    exitCode |= task_no;
+    status = rtems_message_queue_send(Q_id, &exitCode, 4);
+    if (status != RTEMS_SUCCESSFUL) {
+        printk("[TASK %d] Failed to rtems_message_queue_send, status: %d\n", task_no, status);
+    }
+    rtems_task_delete(RTEMS_SELF);
+}