bhyve: uniform printf format string newlines

Some of the printf statements only use LF to get a newline. However, a CR character is also required for the serial console to print debug logs in a nice way.
Fix those code locations that only use LF, by adding a CR character.

Reviewed by: markj, aleksandr.fedorov@itglobal.com
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D22552