Sample: Trace_event: Correct the comments

The commit 889204278ccf ("tracing: Update trace-event-sample with
TRACE_SYSTEM_VAR documentation") changed TRACE_SYSTEM to 'sample-trace',
but didn't make the according change of its name in the comments.

Link: http://lkml.kernel.org/r/1443599650-23680-1-git-send-email-zhang.chunyan@linaro.org

Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

samples/trace_events/trace-events-sample.h

@@ -4,14 +4,14 @@
  *
  * The define_trace.h below will also look for a file name of
  * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
- * In this case, it would look for sample.h
+ * In this case, it would look for sample-trace.h
  *
  * If the header name will be different than the system name
  * (as in this case), then you can override the header name that
  * define_trace.h will look up by defining TRACE_INCLUDE_FILE
  *
  * This file is called trace-events-sample.h but we want the system
- * to be called "sample". Therefore we must define the name of this
+ * to be called "sample-trace". Therefore we must define the name of this
  * file:
  *
  * #define TRACE_INCLUDE_FILE trace-events-sample
@@ -106,7 +106,7 @@
  *
  *         memcpy(__entry->foo, bar, 10);
  *
- *   __dynamic_array: This is similar to array, but can vary is size from
+ *   __dynamic_array: This is similar to array, but can vary its size from
  *         instance to instance of the tracepoint being called.
  *         Like __array, this too has three elements (type, name, size);
  *         type is the type of the element, name is the name of the array.