ethdev: do not use get xstats names by IDs to obtain count
ethdev: do not use get xstats names by IDs to obtain count

Relax requirements on get xstats names by IDs. After the patch
corresponding the driver operation is called with non-NULL ids
and xstats_names parameters only.

Signed-off-by: Andrew Rybchenko <4155e7bf8e0185127625dac6d84336299844982f@oktetlabs.ru>
Acked-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>

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