selftests/hid: fix mypy complains

No code change, only typing information added/ignored

Acked-by: Jiri Kosina <jkosina@suse.com>
Link: https://lore.kernel.org/r/20231206-wip-selftests-v2-14-c0350c2f5986@kernel.org


Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>