drm/bridge: lt9611: simplify video timings programming

Inline calculated values to simplify the calculation in
lt9611_mipi_video_setup().

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230118081658.2198520-11-dmitry.baryshkov@linaro.org