Pull together all the pr_*_once() functions we currently support.
For err and warn add a "%s:%d ", FILE, LINE prefix to the log
entry to make it more valuable. Some drivers use the function with
the same log message multiple times.
Leave info(rmational) messages alone as we print them for, e.g. driver
versions etc.
Sponsored by: The FreeBSD Foundation
MFC after: 3 days