[bhnd] Add logging macros to BHND.

There are 5 logging levels:

• ERROR
• WARN
• INFO
• DEBUG
• TRACE

There are 2 logging context:

• with
• without device

DEBUG and TRACE records are printed only if bootverbose.
Logging records are printed with source code line information if acceptable
logging level is DEBUG or TRACE.

Submitted by: Michael Zhilin <mizhka@gmail.com>
Differential Revision: https://reviews.freebsd.org/D6247