[media] radio-sf16fmi: Set frequency during init

Set freqency during initialization to fix v4l2-compliance error.
This also fixes VIDIOC_G_FREQUENCY always returning zero (broken by me during LM7000 conversion).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>