Relax signal assertion.

Informs, in debug mode only, that a signal wait violated the HSA
spec with regard to the consuming agents list.  This list is used
for optimized signal type selection.

Change-Id: I5879f8f822d01af504ab913482b2532feb00be98

runtime/hsa-runtime/core/runtime/default_signal.cpp

@@ -88,7 +88,7 @@ hsa_signal_value_t DefaultSignal::WaitRelaxed(hsa_signal_condition_t condition,
   bool condition_met = false;
   int64_t value;
 
-  assert(!g_use_interrupt_wait && "Use of non-host signal in host signal wait API.");
+  debug_warning(!g_use_interrupt_wait && "Use of non-host signal in host signal wait API.");
 
   timer::fast_clock::time_point start_time, time;
   start_time = timer::fast_clock::now();