perf pmu: Fix function name in comment, its get_cpuid_str(), not get_cpustr()

get_cpuid_str() is used in tools/perf/arch/xxx/util/header.c,
fix the name in comment.
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lore.kernel.org/lkml/1588141992-48382-1-git-send-email-zhangshaokun@hisilicon.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/pmu-events.h

@@ -26,7 +26,7 @@ struct pmu_event {
  * Map a CPU to its table of PMU events. The CPU is identified by the
  * cpuid field, which is an arch-specific identifier for the CPU.
  * The identifier specified in tools/perf/pmu-events/arch/xxx/mapfile
- * must match the get_cpustr() in tools/perf/arch/xxx/util/header.c)
+ * must match the get_cpuid_str() in tools/perf/arch/xxx/util/header.c)
  *
  * The  cpuid can contain any character other than the comma.
  */