Moved device code to mimic cuda header behavior

1. All fp32, fp64 math device/host functions should be in math_functions.h/.cpp
2. All fp32, fp64 fast math intrinsics for device/host functions should be in device_functions.h/.cpp
3. All the device code implementations should be in device_util.h/.cpp
4. Hence, made changes appropriately by moving code and creating new header files
5. Added math_functions.cpp/.h
6. Changed #ifndef signature to make sure no conflicts between headers with same names in hip/hip_runtime.h and hip/hcc_detail/hip_runtime.h
7. Changed tests to fit the code changes, making them to include appropriate headers
8. Added math_functions.cpp to CMakeLists.txt
9. Some of the tests are still broken, mostly host math functions will fix them in next commit
10. TODO: FIX compilation issues for host math functions

Change-Id: I7a17637d7e294a7d224ffba932c1a08668febd26


[ROCm/hip commit: b723169ee9]

projects/hip/tests/src/deviceLib/hip_ballot.cpp

@@ -25,8 +25,8 @@ THE SOFTWARE.
 
 #include <iostream>
 
-#include "hip/hip_runtime.h"
-#include "hip/device_functions.h"
+#include <hip/hip_runtime.h>
+#include <hip/device_functions.h>
 
 #define HIP_ASSERT(x) (assert((x)==hipSuccess))