r300: nir pass to lower indirect regression
Commit 20ab7046 leads to increase in number of instructions in some shaders at r300 hardware.
Specifically this pushes the glamor/82.shader_test
from shader-db and also two piglits spec@glsl-1.20@execution@fs-vec4-const-array-indirect-access-128-elements
and spec@glsl-1.10@execution@glsl-fs-uniform-array-7
over the instruction limit edge. This was tested with RV530.
In the case of the glamor shader the tgsi we get before has 421 instructions, while after the change there are 503 instructions.
NIR_DEBUG=print,tgsi logs from right before and after this commit attached. glamor82.tar.xz
CC @tarceri