perf kwork top: Simplify bool conversion

./tools/perf/util/bpf_kwork_top.c:120:53-58: WARNING: conversion to bool not needed here

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230915063832.120274-1-yang.lee@linux.alibaba.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>