nfp: flower: tidy tunnel related private data

nfp: flower: tidy tunnel related private data

Recent additions to the flower app private data have grouped the variables
of a given feature into a struct and added that struct to the main private
data struct.

In keeping with this, move all tunnel related private data to their own
struct. This has no affect on functionality but improves readability and
maintenance of the code.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>