hipHostRegister and hipHostMalloc refactor.

Note hipHostMalloc (not hipHostAlloc or hipMallocHost).
 -  the hipHost* is used for all HIP APIs dealing with Host memory.
    (including hipHostMalloc, hipHostFree, hipHostRegister,
hipHostUnregister, hipHostGetFlags, hipHostGetDevicePointer).
  - hipMallocHost is consistent with "hipMalloc" for allocating device
    memory.  Enumerations hipHostMalloc* also used as optional
    flags parm to hipHostMalloc.

tests/src/hipHostAlloc.cpp

@@ -42,9 +42,9 @@ if(prop.canMapHostMemory != 1){
 //std::cout<<"Exiting..."<<std::endl;
 }
 
-HIPCHECK(hipHostAlloc((void**)&A, SIZE, hipHostAllocWriteCombined | hipHostAllocMapped));
-HIPCHECK(hipHostAlloc((void**)&B, SIZE, hipHostAllocDefault));
-HIPCHECK(hipHostAlloc((void**)&C, SIZE, hipHostAllocMapped));
+HIPCHECK(hipHostMalloc((void**)&A, SIZE, hipHostMallocWriteCombined | hipHostMallocMapped));
+HIPCHECK(hipHostMalloc((void**)&B, SIZE, hipHostMallocDefault));
+HIPCHECK(hipHostMalloc((void**)&C, SIZE, hipHostMallocMapped));
 
 HIPCHECK(hipHostGetDevicePointer((void**)&Ad, A, 0));
 HIPCHECK(hipHostGetDevicePointer((void**)&Cd, C, 0));