panvk: Don't lower load_blend_const_color_rgba

We use blend shaders, so load_blend_const_color_rgba should
not be present in the fragment shader. We might want to re-introduce
this code if we decide to specialize fragment shaders when the
blend configuration is static, but let's drop it for now.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: Lars-Ivar Hesselberg Simonsen <lars-ivar.simonsen@arm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32415>

src/panfrost/vulkan/panvk_vX_shader.c

@@ -89,9 +89,6 @@ panvk_lower_sysvals(nir_builder *b, nir_instr *instr, void *data)
    case nir_intrinsic_load_base_instance:
       val = load_sysval(b, graphics, bit_size, vs.base_instance);
       break;
-   case nir_intrinsic_load_blend_const_color_rgba:
-      val = load_sysval(b, graphics, bit_size, blend.constants);
-      break;
    case nir_intrinsic_load_noperspective_varyings_pan:
       /* TODO: use a VS epilog specialized on constant noperspective_varyings
        * with VK_EXT_graphics_pipeline_libraries and VK_EXT_shader_object */