V4L/DVB (6965): tda18271: fix analog tuning regression caused by earlier changeset

An earlier patch, "tda18271: fail table lookups if frequency is out of range"
broke analog support on certain hardware.  This patch fixes that problem, by
allowing the RF_CAL byte to be set to the maximum value, in cases of the
frequency being out of range.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>