nv_copy_image-simple: Use red instead of green

This demonstrates an issue with the iris driver. It does not account for the automatic fast clearing behavior seen on TGL when copy operations are performed.

Copying red onto dark red is enough to engage the automatic clearing behavior because hardware is reinterpreting the floating point clear values to the format chosen by BLORP (UINT), then seemingly clamping to the 8bit-per-channel maximum of 255. So, the source value of 1.0 becomes 255 and the destination clear value of 0.5 becomes 255. Because the pixels written match the destination clear value and the area is large enough, some (if not all) get converted to fast cleared blocks.

Ref: mesa#3732 (closed)