compiler/lower_64bit_packing: rename the pass to be more generic

It can do 32-bit packing too now.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_nir.c

@@ -586,7 +586,7 @@ brw_nir_optimize(nir_shader *nir, const struct brw_compiler *compiler,
                              nir_lower_dfract |
                              nir_lower_dround_even |
                              nir_lower_dmod);
-      OPT(nir_lower_64bit_pack);
+      OPT(nir_lower_pack);
    } while (progress);
 
    return nir;