swscale/utils: remove useless ()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 554e913fd7acc9da02ddac2c5ce9487f7f633c92)
swscale/utils: check chroma width for fast bilinear scaler

Fixes artifacts where fast bilinear was used for downscaling chroma

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 037fc3b054b10aee0f11fdbe835e5dffa8e95b37)