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.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>