V4L/DVB (4654): Added module parameter force_lna_activation

Added a module parameter for force the activation of any LNA on a board.
Suggest by Steve Toth.

Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>