nir: Add a face_sysval argument to nir_lower_two_sided_color

This is needed for handling drivers that use an input for loading the
face, for example Panfrost with Midgard GPUs.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Tested-by: Urja Rannikko <urjaman@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5915>

src/compiler/nir/nir.h

@@ -4374,7 +4374,7 @@ void nir_lower_point_size_mov(nir_shader *shader,
 
 bool nir_lower_frexp(nir_shader *nir);
 
-void nir_lower_two_sided_color(nir_shader *shader);
+void nir_lower_two_sided_color(nir_shader *shader, bool face_sysval);
 
 bool nir_lower_clamp_color_outputs(nir_shader *shader);
 

src/compiler/nir/nir_lower_two_sided_color.c

@@ -195,7 +195,7 @@ nir_lower_two_sided_color_impl(nir_function_impl *impl,
 }
 
 void
-nir_lower_two_sided_color(nir_shader *shader)
+nir_lower_two_sided_color(nir_shader *shader, bool face_sysval)
 {
    lower_2side_state state = {
       .shader = shader,