ethdev: check maximum number of queues for statistics

Arrays inside rte_eth_stats have size=RTE_ETHDEV_QUEUE_STAT_CNTRS.
Some devices report more queues than that and this code blindly uses
the reported number of queues by the device to fill those arrays up.
This patch fixes the problem using MIN between the reported number of
queues and RTE_ETHDEV_QUEUE_STAT_CNTRS.

Fixes: ce757f5c9a4d ("ethdev: new method to retrieve extended statistics")

Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
Reviewed-by: Olivier Matz <olivier.matz@6wind.com>