perf hists: Fix variable name's inconsistency in hists__for_each() macro

perf hists: Fix variable name's inconsistency in hists__for_each() macro

Variable names are inconsistent in hists__for_each macro().

Due to this inconsistency, the macro replaces its second argument with
"fmt" regardless of its original name.

So far it works because only "fmt" is passed to the second argument.
However, this behavior is not expected and should be fixed.

Fixes: 3fb6b418b8e3 ("perf hists: Introduce hists__for_each_format macro")
Fixes: 1856079db676 ("perf hists: Introduce hists__for_each_sort_list macro")
Signed-off-by: Yuya Fujita <fujita.yuya@fujitsu.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/OSAPR01MB1588E1C47AC22043175DE1B2E8520@OSAPR01MB1588.jpnprd01.prod.outlook.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>