tunneling: Remove struct tnl_vport and tnl_ops.

tunneling: Remove struct tnl_vport and tnl_ops.

After flow based tunneling, kernel tunneling is greatly simplified.
There is no need to have extra tunneling layer between vport and
particular protocol.
Following patch removes tunneling struct which make code easy to read.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>