V4L/DVB (7430): tda18271: fix typo in tda18271_calibrate_rf

The internal calibration signal must be set on the cal pll.

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