nir: Add lowering support for 64-bit operations to software

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.h

@@ -3204,7 +3204,8 @@ typedef enum {
    nir_lower_dceil = (1 << 5),
    nir_lower_dfract = (1 << 6),
    nir_lower_dround_even = (1 << 7),
-   nir_lower_dmod = (1 << 8)
+   nir_lower_dmod = (1 << 8),
+   nir_lower_fp64_full_software = (1 << 9),
 } nir_lower_doubles_options;
 
 bool nir_lower_doubles(nir_shader *shader, nir_lower_doubles_options options);