V4L/DVB (6963): tda18271: store IF frequency in a u16 instead of u32

Store IF Frequency in a u16 instead of a u32.  Multiply by 1000 before use.

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