LinuxKPI: lockdep_assert: wrong 'cond' used in WARN_ON MACRO

'cond' in WARN_ON need be bracketed,
otherwise it is wrong for multiple conditions.

Reviewed by: wulf
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D44604

(cherry picked from commit 21f4cf5ccf87fd15d4d71f89d4c3ecab13f26146)