Plane validation uses an API drm_calc_scale which will
return src/dst value as a scale ratio.

when viewing the range on a scale the values should fall in as

Upscale ratio < Unity scale < Downscale ratio for src/dst formula

Fix the min and max scale ratios to suit the API accordingly.
Signed-off-by: Kalyan Thota <kalyan_t@codeaurora.org>
Tested-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>