nir: Make nir_deref_instr_build/get_const_offset actually use size_align.

I think this was copy-and-paste mistake -- nir_opt_large_constants was
passing in glsl_get_natural_size_align_bytes() given brw_nir.c's arguments
to the opt pass.

I wanted to reuse this function for handling constant offsets of arrays of
images in V3D.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Rob Clark <robdclark@gmail.com>

src/compiler/nir/nir_deref.c

                       glsl_type_size_align_func size_align)
 {
    unsigned elem_size, elem_align;
-   glsl_get_natural_size_align_bytes(elem_type, &elem_size, &elem_align);
+   size_align(elem_type, &elem_size, &elem_align);
    return ALIGN_POT(elem_size, elem_align);
 }
 
    unsigned offset = 0;
    for (unsigned i = 0; i <= field_idx; i++) {
       unsigned elem_size, elem_align;
-      glsl_get_natural_size_align_bytes(glsl_get_struct_field(struct_type, i),
-                                        &elem_size, &elem_align);
+      size_align(glsl_get_struct_field(struct_type, i), &elem_size, &elem_align);
       offset = ALIGN_POT(offset, elem_align);
       if (i < field_idx)
          offset += elem_size;