crypto: Cleanup mtx_init() calls.

Don't pass the same name to multiple mutexes while using unique types
for WITNESS. Just use the unique types as the mutex names.

Reviewed by: markj
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D32740

(cherry picked from commit 4e057806cf56b238a0a3ef7af140f447d7b67ab5)