Fix r600/nir for Cayman
This series fixes most issues in the NIR backend for Cayman. What is missing is using hardware FP64 and some ARB_shader_image_load_store piglit tests make the hardware crash hard resulting in the need for a reboot. Apart from these two issues, the rate of passing piglit and dEQP-gles tests is in favor of the NIR code path.
The series is on top of !10577 (merged) that fixes a sloppyness in the instruction lowering filter.
Edited by Gert Wollny