media: staging: media: ipu3: Fix AF x_start position when rightmost stripe is used

media: staging: media: ipu3: Fix AF x_start position when rightmost stripe is used

For the AF configuration, if the rightmost stripe is used, the AF scene
will be at the incorrect location of the sensor.

The AF coordinate may be set to the right part of the sensor. This
configuration would lead to x_start being greater than the
down_scaled_stripes offset and the leftmost stripe would be disabled
and only the rightmost stripe is used to control the AF coordinate. If
the x_start doesn't perform any adjustments, the AF coordinate will be
at the wrong place of the sensor since down_scaled_stripes offset
would be the new zero of the coordinate system.

In this patch, if only the rightmost stripe is used, x_start should
minus down_scaled_stripes offset to maintain its correctness of AF
scene coordinate.

Signed-off-by: Kate Hsuan <hpa@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>