V4L/DVB (3195): Fix for 64-bit compile warning

- Add the fix for the saa7146 64-bit compile warning (again). This time with
comments and checked by Johannes Stezenbach.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>