Fix ifndef guard in hip_fp16.h

Change-Id: I0215556e7aa98a74e8a984e4de3fb6e8cafdfb24


[ROCm/hip commit: 71447dacad]

projects/hip/include/hip/hip_fp16.h

@@ -20,7 +20,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
-#ifdef HIP_INCLUDE_HIP_HIP_FP16_H
+#ifndef HIP_INCLUDE_HIP_HIP_FP16_H
 #define HIP_INCLUDE_HIP_HIP_FP16_H
 
 #include <hip/hip_common.h>