radv: Support nir_intrinsic_load_global_constant.

SPIR-V parsing can result in some direct constant usage for shader
records. Lower this early to a global based intrinsic so that it
doesn't interfere with the later 32-bit offset based constants
for scratch usage.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12592>

src/amd/compiler/aco_instruction_selection_setup.cpp

@@ -805,6 +805,7 @@ init_context(isel_context* ctx, nir_shader* shader)
                case nir_intrinsic_load_ubo:
                case nir_intrinsic_load_ssbo:
                case nir_intrinsic_load_global:
+               case nir_intrinsic_load_global_constant:
                case nir_intrinsic_vulkan_resource_index:
                case nir_intrinsic_get_ssbo_size:
                   type = nir_dest_is_divergent(intrinsic->dest) ? RegType::vgpr : RegType::sgpr;