habanalabs: add terminating NULL to attrs arrays

Arrays of struct attribute are expected to be NULL terminated.
This is required by API methods such as device_add_groups.
This fixes a crash when loading the driver for Goya device.

Signed-off-by: Dafna Hirschfeld <dhirschfeld@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>