media: vidtv: fix DVB-S/S2 tuning logic

Satellite setups are different than terrestrial and cable ones,
as there is a device coupled at the antenna, called LNBf, which
converts the frequency from a GHz range at C-Band or Ku-Band
into an intermediate frequency at S-Band (ranging up to ~2GHz).

There are several different models of LNBf, with different
IF conversions, but the most common nowadays is called
Universal LNBf. Those got their frequency ranges extended in the
past, when Astra 19.2E sattellite was launched.

The universal LNBf has two local oscilators:

	- 9.75 GHz
	- 10.6 GHz

The first one is used when the frequency is between 10.7 GHz
up to 11.7 GHz. The second one is for frequencies between
11.7 GHz to 12.75 GHz.

With that, the IF signal will be at 950 MHz to 2,150 MHz range.

Add support for doing the above math, and make clear that
the frequencies expected by the driver should be at Ku-Band
range.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>