intel/rt: Add support for shader buffer record memory

Most of the work for this is done for us by spirv_to_nir which gives us
a load_global from a memory address based on the shader_record_ptr
system values.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7356>

src/intel/compiler/brw_nir_rt.c

@@ -178,10 +178,12 @@ lower_rt_io_and_scratch(nir_shader *nir)
    /* Now patch any derefs to I/O vars */
    NIR_PASS_V(nir, lower_rt_io_derefs);
 
-   /* Finally, lower any remaining function_temp access to 64-bit global
-    * memory access.
+   /* Finally, lower any remaining function_temp and mem_constant access to
+    * 64-bit global memory access.
     */
-   NIR_PASS_V(nir, nir_lower_explicit_io, nir_var_function_temp,
+   NIR_PASS_V(nir, nir_lower_explicit_io,
+              nir_var_function_temp |
+              nir_var_mem_constant,
               nir_address_format_64bit_global);
 }