Enable ACPICA mutex debugging in INVARIANTS case.

This lets us detect lock order reversal in ACPICA code to avoid deadlock.

sys/contrib/dev/acpica/include/platform/acfreebsd.h

@@ -203,6 +203,10 @@
 
 #define DEBUGGER_THREADING  0   /* integrated with DDB */
 
+#ifdef INVARIANTS
+#define ACPI_MUTEX_DEBUG
+#endif
+
 #else /* _KERNEL */
 
 #if __STDC_HOSTED__