[media] mt9v011: Fixed incorrect value for the first valid column

According to the datasheet (page 8), the first optical clear
pixel-column is not at position 14. The correct/recommended value is 20.
Without this patch there is a dark line on the left side of the image.

Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Johannes Obermaier <johannes.obermaier@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>