mesa: correctly calculate the storage offset for i915

When generating the storage offset for struct members we need
to skip opaque types as they no longer have backing storage.

Fixes: fcbb93e860 ("mesa: stop assigning unused storage for non-bindless opaque types")

V2: simplify since bindless will never be supported in this code

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101983
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/program/ir_to_mesa.cpp

@@ -550,10 +550,8 @@ type_size(const struct glsl_type *type)
       return size;
    case GLSL_TYPE_SAMPLER:
    case GLSL_TYPE_IMAGE:
+      return 0;
    case GLSL_TYPE_SUBROUTINE:
-      /* Samplers take up one slot in UNIFORMS[], but they're baked in
-       * at link time.
-       */
       return 1;
    case GLSL_TYPE_ATOMIC_UINT:
    case GLSL_TYPE_VOID: