perf ftrace: Fix display for range of the first bucket

When min_latency is not given, it prints 0 - 0.  It should be 0 - 1.

Before:

  $ sudo ./perf ftrace latency -a -T do_futex sleep 1
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -    0 us |        321 | ###########                                    |
  ...

After:

  $ sudo ./perf ftrace latency -a -T do_futex sleep 1
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -    1 us |        699 | ############                                   |
  ...

Fixes: 08b875b ("perf ftrace latency: Introduce --min-latency to narrow down into a latency range")
Reviewed-by: Gabriele Monaco <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Tested-by: Gabriele Monaco <[email protected]
Cc: Adrian Hunter <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: namhyung

tools/perf/builtin-ftrace.c

@@ -840,7 +840,7 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
 	bar_len = buckets[0] * bar_total / total;
 
 	printf("  %4d - %4d %s | %10d | %.*s%*s |\n",
-	       0, min_latency, use_nsec ? "ns" : "us",
+	       0, min_latency ?: 1, use_nsec ? "ns" : "us",
 	       buckets[0], bar_len, bar, bar_total - bar_len, "");
 
 	for (i = 1; i < NUM_BUCKET - 1; i++) {