lavapipe: don't clamp index buffer size for null index buffer draws

this should execute however many draws the user is trying to execute

cc: mesa-stable

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28656>

src/gallium/frontends/lavapipe/lvp_execute.c

@@ -2737,7 +2737,7 @@ static void handle_index_buffer2(struct vk_cmd_queue_entry *cmd,
       state->index_buffer = lvp_buffer_from_handle(ib->buffer)->bo;
    } else {
       state->index_size = 4;
-      state->index_buffer_size = sizeof(uint32_t);
+      state->index_buffer_size = UINT32_MAX;
       state->index_offset = 0;
       state->index_buffer = state->device->zero_buffer;
    }