V4L/DVB (6719): ivtv: ivtv-yuv clean-up + source cropping bug-fix

ivtv-yuv code clean up & reformat. Includes minor changes to some debug lines.

Also fixes a bug found during the reformatting, which would cause the
incorrect amount of yuv data to be sent to the card if source cropping
coordinates were used.

Apart from the bug-fix, there should be no functional difference to the
previous version.
Signed-off-by: NIan Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>