stacktrace: Get rid of unneeded '!!' pattern

My commit b0c51f1 ("stacktrace: Don't skip first entry on
noncurrent tasks") adds one or zero to skipnr by "!!(current == tsk)".

But the C99 standard says:

  The == (equal to) and != (not equal to) operators are
  ...
  Each of the operators yields 1 if the specified relation is true and 0
  if it is false.

So there is no need to prepend the above expression by "!!" -- remove it.

Reported-by: Joe Perches <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Jiri Slaby

kernel/stacktrace.c

@@ -142,7 +142,7 @@ unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
 		.store	= store,
 		.size	= size,
 		/* skip this function if they are tracing us */
-		.skip	= skipnr + !!(current == tsk),
+		.skip	= skipnr + (current == tsk),
 	};
 
 	if (!try_get_task_stack(tsk))
@@ -300,7 +300,7 @@ unsigned int stack_trace_save_tsk(struct task_struct *task,
 		.entries	= store,
 		.max_entries	= size,
 		/* skip this function if they are tracing us */
-		.skip	= skipnr + !!(current == task),
+		.skip	= skipnr + (current == task),
 	};
 
 	save_stack_trace_tsk(task, &trace);