MFC: r233423

MFC: r233423

Initialize the mutexes used for the NVM and the swflag as MTX_DUPOK in
order to avoid otherwise harmless witness warnings when these are acquired
at the same time and due to both using MTX_NETWORK_LOCK as their type.
The right fix actually would be to use different, descriptive types for
these. However, the latter would require undesirable changes to the shared
code base. Another approach would be to just supply NULL as the type, which
was deemed as less desirable though as it would cause the unique but cryptic
name also to be used for the type and to diverge from the type used by other
network device drivers.

git-svn-id: svn://svn.freebsd.org/base/stable/9@233725 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f