Corrected type in lock descriptions

There was a small type ("eference" vs "reference") in the description of the "(r)" comment.

sys/sys/procdesc.h

@@ -47,7 +47,7 @@
  * Locking key:
  * (c) - Constant after initial setup.
  * (p) - Protected by the process descriptor mutex.
- * (r) - Atomic eference count.
+ * (r) - Atomic reference count.
  * (s) - Protected by selinfo.
  * (t) - Protected by the proctree_lock
  */