net: fix comment in IPv6 header

The comment got it wrong. The payload length field
does not include the fixed IPv6 header size.

Fixes: 7eca7f7 ("net: add missing endianness annotations")
Fixes: af75078 ("first public release")
Cc: stable@dpdk.org

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

lib/librte_net/rte_ip.h

@@ -384,7 +384,7 @@ rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, const void *l4_hdr)
  */
 struct rte_ipv6_hdr {
 	rte_be32_t vtc_flow;	/**< IP version, traffic class & flow label. */
-	rte_be16_t payload_len;	/**< IP packet length - includes header size */
+	rte_be16_t payload_len;	/**< IP payload size, including ext. headers */
 	uint8_t  proto;		/**< Protocol, next header. */
 	uint8_t  hop_limits;	/**< Hop limits. */
 	uint8_t  src_addr[16];	/**< IP address of source host. */