app/procinfo: fix const pointer in collectd format

app/procinfo: fix const pointer in collectd format

With latest glibc (Fedora Rawhide):
../app/proc-info/main.c: In function 'collectd_resolve_cnt_type':
../app/proc-info/main.c:689:26: warning: initialization discards
	'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
  689 |         char *type_end = strrchr(cnt_name, '_');
      |                          ^~~~~~~

Fixes: 2deb6b5246d7 ("app/procinfo: add collectd format and host id")
Cc: stable@dpdk.org
Signed-off-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Chengwen Feng <fengchengwen@huawei.com>