V4L/DVB (6347): ivtv: fix video mute when radio is used

When the radio is active the video should be muted when a capture
starts. However, this was done at the wrong time and the mute settings
were overwritten when cx2341x_update was called.

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