radv/shader_info: start gathering tess output info (v2)

radv/shader_info: start gathering tess output info (v2)

This gathers the ls outputs written by the vertex shader,
and the tcs outputs, these are needed to calculate certain
tcs parameters.

These have to be separate for combined gfx9 shaders.

This is a bit pessimistic compared to the nir pass,
as we don't work out the individual slots for tcs outputs,
but I actually thing it should be fine to just mark the whole
thing used here.

v2: move to radv, handle clip dist (Samuel),
    handle compacts and patchs properly.
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>