Modify hipMalloc to take size of 0 and return NULL pointer for it.

Modify hipMemoryAllocate test for this change.

Change-Id: I884aee0cd5fe0c60aebb4cb37cdbb4833c5bd0c7

tests/src/runtimeApi/memory/hipMemoryAllocate.cpp

@@ -21,7 +21,7 @@ THE SOFTWARE.
 #define SIZE 1024*1024*256
 
 int main(){
-    float *Ad, *B, *Bd, *Bm, *C, *Cd;
+    float *Ad, *B, *Bd, *Bm, *C, *Cd, *ptr_0;
     B = (float*)malloc(SIZE);
     hipMalloc((void**)&Ad, SIZE);
     hipHostMalloc((void**)&B, SIZE);
@@ -31,12 +31,15 @@ int main(){
 
     hipHostGetDevicePointer((void**)&Cd, C, 0/*flags*/);
 
+    HIPCHECK_API(hipMalloc((void**)&ptr_0,0), hipSuccess);
+
     HIPCHECK_API(hipFree(Ad) ,  hipSuccess);
     HIPCHECK_API(hipHostFree(Ad) , hipErrorInvalidValue);
 
     HIPCHECK_API(hipFree(B)  , hipErrorInvalidDevicePointer); // try to hipFree on malloced memory
     HIPCHECK_API(hipFree(Bd) , hipErrorInvalidDevicePointer);
     HIPCHECK_API(hipFree(Bm) , hipErrorInvalidDevicePointer);
+    HIPCHECK_API(hipFree(ptr_0) , hipSuccess);
     HIPCHECK_API(hipHostFree(Bd) , hipSuccess);
     HIPCHECK_API(hipHostFree(Bm) , hipSuccess);