media: vimc: Update device configuration in the documentation

Since commit 9b4a9b31 ("media: vimc: Enable set resolution at the
scaler src pad") the configuration in the documentation does not work.
Replace it with the configuration described in that commit.

Signed-off-by: Dafna Hirschfeld <dafna@fastmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>