avutil/colorspace: Remove RGB_TO_Y/U/V

They are unused and colorspace.h is not a installed header
Found-by: Timo Rothenpieler <timo@rothenpieler.org>
Reviewed-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/colorspace.h

@@ -84,18 +84,6 @@ static inline int C_JPEG_TO_CCIR(int y) {
 }
 
 
-#define RGB_TO_Y(r, g, b) \
-((FIX(0.29900) * (r) + FIX(0.58700) * (g) + \
-  FIX(0.11400) * (b) + ONE_HALF) >> SCALEBITS)
-
-#define RGB_TO_U(r1, g1, b1, shift)\
-(((- FIX(0.16874) * r1 - FIX(0.33126) * g1 +         \
-     FIX(0.50000) * b1 + (ONE_HALF << shift) - 1) >> (SCALEBITS + shift)) + 128)
-
-#define RGB_TO_V(r1, g1, b1, shift)\
-(((FIX(0.50000) * r1 - FIX(0.41869) * g1 -           \
-   FIX(0.08131) * b1 + (ONE_HALF << shift) - 1) >> (SCALEBITS + shift)) + 128)
-
 #define RGB_TO_Y_CCIR(r, g, b) \
 ((FIX(0.29900*219.0/255.0) * (r) + FIX(0.58700*219.0/255.0) * (g) + \
   FIX(0.11400*219.0/255.0) * (b) + (ONE_HALF + (16 << SCALEBITS))) >> SCALEBITS)