We can't display the UI box saying that we are slow in the reader
thread.  That will make 'perf top' even slower and the user even more
angry ;-)

Move the UI box message from the reader thread to the UI thread and
change it to a helpline, so there's no need to 'press any key'.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-x4k0iuw7tt6mywsaguq6jfwu@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>