Fix regression in poll() and select()

With the fix that made poll() and select() block if read would block
 caused a slight regression in rasdaemon, as it needed that kind
 of behavior. Add a way to make that behavior come back by writing
 zero into the "buffer_percentage", which means to never block on read.
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Merge tag 'trace-v6.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fix from Steven Rostedt:
 "Fix regression in poll() and select()

  With the fix that made poll() and select() block if read would block
  caused a slight regression in rasdaemon, as it needed that kind of
  behavior. Add a way to make that behavior come back by writing zero
  into the 'buffer_percentage', which means to never block on read"

* tag 'trace-v6.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Fix poll() and select() do not work on per_cpu trace_pipe and trace_pipe_raw

kernel/trace/trace.c

@@ -9148,9 +9148,6 @@ buffer_percent_write(struct file *filp, const char __user *ubuf,
 	if (val > 100)
 		return -EINVAL;
 
-	if (!val)
-		val = 1;
-
 	tr->buffer_percent = val;
 
 	(*ppos)++;