media: cx18: fix format compliance issues

This properly fills in all the format fields and calculates the
width and height correctly.

Esp. the minimum width and height was wrong.

When changing the standard the width and height also have to be
reset to the corresponding default width/height for the chosen
standard.

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