habanalabs: expose only valid debugfs nodes

In case security is enabled on the device, some debugfs nodes will
fail. Hence, we do not expose them.

Signed-off-by: Ofir Bitton <obitton@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>