MFC r276532 and r276626:

MFC r276532 and r276626:
The "cnputs_mtx" mutex must be allowed to recurse. Debug prints and/or
witness printouts in the console driver clients can cause this mutex
to recurse by calls to "printf()" from witness for example. In
particular this can happen if "debug.witness.skipspin=0" is set in the
boot environment.

git-svn-id: svn://svn.freebsd.org/base/stable/8@276971 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f