radv/ac: canonicalize the output for 32-bit float min/max.

radv/ac: canonicalize the output for 32-bit float min/max.

This fixes:
dEQP-VK.glsl.builtin.precision.min.*
dEQP-VK.glsl.builtin.precision.max.*
dEQP-VK.glsl.builtin.precision.clamp.*

The problem is the hw doesn't compare denorms properly,
so we have to flush them, even though the spec says
flushing is optional, if you don't flush the results
should be correct.

The -pro driver changes the shader float mode,
it would be nice if llvm could grow that perhaps.

Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>