Currently SFN, TNUMT and TNPC registers use separate enums for
tunnel_port.

Create one enum with a neutral name and use it.
Remove the enums that are not currently required.

The next patches add two more registers that contain tunnel_port field,
the new enum can be used for them also.
Signed-off-by: NAmit Cohen <amcohen@nvidia.com>
Reviewed-by: NPetr Machata <petrm@nvidia.com>
Signed-off-by: NIdo Schimmel <idosch@nvidia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>