net/mlx5: add VXLAN to flow prepare routine
net/mlx5: add VXLAN to flow prepare routine

The e-switch Flow prepare function is updated to support VXLAN
encapsulation/and decapsulation actions. The function calculates
buffer size for Netlink message and Flow description structures,
including optional ones for tunneling purposes.

Suggested-by: Adrien Mazarguil <9d39ea493ca46c560334f650ac5d4b5ffbcb5cf0@6wind.com>
Signed-off-by: Viacheslav Ovsiienko <5b8db9bb93a9a9aefc8828f79604d1fe963a53dd@mellanox.com>
Acked-by: Yongseok Koh <76b37c91816d73ef9cf709e3e83a68f2d162f1e2@mellanox.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk