After doing a driver callout to fill in the driver specific
parts of struct rte_eth_stats, rte_eth_stats_get() overwrites
the rx_nombuf member regardless of whether the driver itself
has assigned a value. Any driver-assigned value should take
priority.
Fixes: af75078fece3 ("first public release")
Signed-off-by: Remy Horton <remy.horton@intel.com>