ipmi: do not omit lun in BMC addresses

From: Yuri <yuri_at_aetern.org>
Date: Tue, 28 Jun 2022 17:11:24 UTC
Another simple review for ipmi driver, which fixes sensors on some
systems where they were put on non-0 lun.  This was the only difference
with linux driver here, where the sensors worked.

https://reviews.freebsd.org/D35612