[NAN] Add transport type for NAN. [DO NOT MERGE]

Add TRANSPORT_WIFI_NAN - specifies a peer-to-peer Wi-Fi NAN data
connectivity request.

While NAN uses Wi-Fi L1 PHY and part of the MAC - it is a different
protocol and constitutes a different transport.

(cherry-pick of commit 7b84987a)

Bug: 26564277
Change-Id: I975ebc72d8f97a592d18038b3d6465b7a40efa75