nir: Remove the const_offset from nir_tex_instr

When NIR was originally drafted, there was no easy way to determine if
something was constant or not.  The result was that we had lots of
special-casing for constant values such as this.  Now that load_const
instructions are SSA-only, it's really easy to find constants and this
isn't really needed anymore.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Rob Clark <robclark@gmail.com>

src/compiler/nir/nir_clone.c

@@ -355,7 +355,6 @@ clone_tex(clone_state *state, const nir_tex_instr *tex)
    ntex->is_array = tex->is_array;
    ntex->is_shadow = tex->is_shadow;
    ntex->is_new_style_shadow = tex->is_new_style_shadow;
-   memcpy(ntex->const_offset, tex->const_offset, sizeof(ntex->const_offset));
    ntex->component = tex->component;
 
    ntex->texture_index = tex->texture_index;