hidbus(4): Fix wrong assertion of bus

Reviewed by: wulf
Fixes: 4151ac9f1292 hidbus(4): Use generic hid methods to ...
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D45496

(cherry picked from commit 4eb82e65a73f6cd180700bb8ae47227a553f94ed)