V4L/DVB (6346): ivtvfb: YUV output size fix when ivtvfb is not loaded

If the ivtvfb module isn't loaded, the valid YUV output area should be set to
full-screen. This patch fixes the case where the valid output area was not
reset when the output broadcast format was changed from NTSC to PAL. This
resulted in output being limited to the top 480 lines of the display.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>