This fixes the rendering of the scan visor in Metroid Prime 2: Echoes,
as seen in https://fifoci.dolphin-emu.org/dff/mp2-scanner/
The alpha channel was off-by-one on Ivy Bridge due to the rounding
after multiplication with colmat. This commit removes this matrix
altogether in most cases, making them simple GLSL swizzles.
This will generate one shader per copy format. For now, it is the same
shader with the colmat hard coded. So it should already improve the GPU
performance a bit, but a rewrite of the shader generator is suggested.
Half of the patch is done by linkmauve1:
VideoCommon: Reorganise the shader writes.