ethdev: add actions to modify TCP header fields

ethdev: add actions to modify TCP header fields

Add actions:
- INC_TCP_SEQ - Increase sequence number in the outermost TCP header.
- DEC_TCP_SEQ - Decrease sequence number in the outermost TCP header.
- INC_TCP_ACK - Increase acknowledgment number in the outermost TCP
		header.
- DEC_TCP_ACK - Decrease acknowledgment number in the outermost TCP
		header.

Original work by Xiaoyu Min.

This patch uses the new approach introduced by [1], using a simple
integer instead of using an action-specific structure for each of
the new actions.

[1] http://patches.dpdk.org/patch/55882/

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>