app/procinfo: fix check on xstats-ids
app/procinfo: fix check on xstats-ids

'parse_xstats_ids()' return 'int'. The return value is assigned to
'nb_xstats_ids' unsigned value, later negative check on this variable is
wrong.

Adding interim 'int' variable for negative check.

Fixes: 7ac16a3660c0 ("app/proc-info: support xstats by ID and by name")
Cc: stable@dpdk.org

Signed-off-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>
Reviewed-by: David Marchand <f28529695cfa9e3e1eb84e7072aa626af4abb18e@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk