net/bnxt: fix xstats query

Fix incorrect memset in bnxt_dev_xstats_get_op.
In bnxt_dev_xstats_get_op(), the PMD is not zeroing the whole
buffer supplied by the application. This can end up passing
junk statistics values to the application when the FW does not
support extended stats on a function.
Fixed to call memset() with correct size.

Fixes: f55e12f ("net/bnxt: support extended port counters")
Cc: stable@dpdk.org

Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>

drivers/net/bnxt/bnxt_stats.c

@@ -741,7 +741,7 @@ int bnxt_dev_xstats_get_op(struct rte_eth_dev *eth_dev,
 					(bp->fw_tx_port_stats_ext_size /
 					 stat_size));
 
-	memset(xstats, 0, sizeof(*xstats));
+	memset(xstats, 0, sizeof(*xstats) * n);
 
 	count = 0;
 	for (i = 0; i < RTE_DIM(bnxt_rx_stats_strings); i++) {