swscale/utils: Simplify scaler name printing code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale/utils: simplify cpu caps printing code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale/utils: remove redundant NULL checks before sws_freeVec()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>