[OpenMP] Fix warnings about unused expressions when OMPT_LOOP_DISPATC…

…H is a no-op. NFC.

This fixes warnings like these:

../runtime/src/kmp_dispatch.cpp:2159:24: warning: left operand of comma operator has no effect [-Wunused-value]
    OMPT_LOOP_DISPATCH(*p_lb, *p_ub, pr->u.p.st, status);
                       ^~~~~
../runtime/src/kmp_dispatch.cpp:2159:31: warning: left operand of comma operator has no effect [-Wunused-value]
    OMPT_LOOP_DISPATCH(*p_lb, *p_ub, pr->u.p.st, status);
                              ^~~~~
../runtime/src/kmp_dispatch.cpp:2159:46: warning: left operand of comma operator has no effect [-Wunused-value]
    OMPT_LOOP_DISPATCH(*p_lb, *p_ub, pr->u.p.st, status);
                                     ~~~~~~~ ^~
../runtime/src/kmp_dispatch.cpp:2159:50: warning: expression result unused [-Wunused-value]
    OMPT_LOOP_DISPATCH(*p_lb, *p_ub, pr->u.p.st, status);
                                                 ^~~~~~

openmp/runtime/src/kmp_dispatch.cpp

@@ -1979,7 +1979,7 @@ int __kmp_dispatch_next_algorithm(int gtid,
 // TODO: implement count
 #else
 #define OMPT_LOOP_END // no-op
-#define OMPT_LOOP_DISPATCH // no-op
+#define OMPT_LOOP_DISPATCH(lb, ub, st, status) // no-op
 #endif
 
 #if KMP_STATS_ENABLED