net: eth_legacy - fix build CMD_PCAP

Fix typo which would cause a build error.

Fixes: 3eaac6307df ("net: introduce packet capture support")

Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
diff --git a/net/eth_legacy.c b/net/eth_legacy.c
index 6e0c058..6870afb 100644
--- a/net/eth_legacy.c
+++ b/net/eth_legacy.c
@@ -365,7 +365,7 @@
 	ret = eth_current->send(eth_current, packet, length);
 #if defined(CONFIG_CMD_PCAP)
 	if (ret >= 0)
-		pcap_post(packet, lengeth, true);
+		pcap_post(packet, length, true);
 #endif
 	return ret;
 }