perf timechart: Remove redundant variable assignment

This patch makes a minor change that removes a redundant variable
assignment. The assignment before the for loop is duplicated by the
initialization within the loop header.

Signed-off-by: Luo Yifan <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-timechart.c

···
 			}
 
 			svg_box(Y, c->start_time, c->end_time, "process3");
-			sample = c->io_samples;
 			for (sample = c->io_samples; sample; sample = sample->next) {
 				double h = (double)sample->bytes / c->max_bytes;