V4L/DVB (7341): ivtv: rename tunerhz to tunertype

There are two tuner types: those for M/N standards and those for all others.
However, M/N standards are not always 60 Hz (PAL-N/Nc are 50 Hz), so rename
the module option accordingly.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>