tvnow: build for linuxtv_tuner when LINUXTV is #define'd else use hdhr_tuner

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
tvnow: fix build for compatibility against libdvbtee v0.2.2

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>