[media] tda8290: change magic LNA config values to enum

Use enum instead of magic values for LNA config in tda8290.
Update tda827x, tda18271 and saa7134 to use the enum too.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>