Fix warning

/home/boud/dev/krita/libs/pigment/KoColorSpace.cpp: In member function ‘QPolygonF KoColorSpace::estimatedTRCXYY() const’:
/home/boud/dev/krita/libs/pigment/KoColorSpace.cpp:200:48: warning: variable length array ‘data2’ is used [-Wvla]

quint8 data2[xyzColorSpace->pixelSize()];