[media] tda10071: do not check tuner PLL lock on read_status()

Tuner PLL lock flag was mapped to FE_HAS_SIGNAL, which is wrong. PLL
lock has nothing to do with received signal. In real life that flag
is always set.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>