linuxkpi: Define DEFINE_WD_CLASS(name) in <linux/ww_mutex.h>
It is defined as a synonymous to DEFINE_WW_CLASS(name).
Reviewed by: manu
Approved by: manu
Differential Revision: https://reviews.freebsd.org/D38151
(cherry picked from commit d9f1cb6774f1785544c2fbeba476d4842967e804)