Sample improvements.

- Enable -O3 for hipDispatchLatency.
- Use nearly-null kernel to prevent it from being optimized away.
- Formatting for hipDispatchLatency.
- Formatting for hipInfo.


[ROCm/hip commit: 1160cefc6d]

projects/hip/samples/1_Utils/hipInfo/hipInfo.cpp

@@ -65,7 +65,7 @@ double bytesToGB(size_t s)
 void printDeviceProp (int deviceId)
 {
     using namespace std;
-    const int w1 = 30;
+    const int w1 = 34;
 
     cout << left;