anv: use helper function to get the buffer size

This ensures we get a properly aligned size for the buffer so we don't
trip over HW limits for push constants.

Closes #3703
Fixes dEQP-VK.robustness.image_robustness.push.* on HSW

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9699>

src/intel/vulkan/anv_cmd_buffer.c

@@ -1269,7 +1269,8 @@ anv_cmd_buffer_push_descriptor_set(struct anv_cmd_buffer *cmd_buffer,
        */
       struct anv_state desc_mem =
          anv_state_stream_alloc(&cmd_buffer->dynamic_state_stream,
-                                layout->descriptor_buffer_size, 32);
+                                anv_descriptor_set_layout_descriptor_buffer_size(layout, 0),
+                                ANV_UBO_ALIGNMENT);
       if (set->desc_mem.alloc_size) {
          /* TODO: Do we really need to copy all the time? */
          memcpy(desc_mem.map, set->desc_mem.map,