V4L/DVB (5673): Fix audio stuttering for saa711x/ivtv when in radio mode.

Signed-off-by: Jose Alberto Reguero <jareguero@telefonica.net>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>