perf timechart: Remove redundant variable assignment

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 <luoyifan@cmss.chinamobile.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241111095209.276332-1-luoyifan@cmss.chinamobile.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>