V4L/DVB (7983): tda18271_calc_rf_cal must return the return value of tda18271_lookup_map

On the TDA18271HD/C1, we perform RF tracking filter correction for VHF low
band, only. If supplied a frequency out of range, the error must be returned
to the caller (tda18271c1_rf_tracking_filter_calibration) so that it can
decide whether or not to write to register EB14, RFC_CPROG[7:0]

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