added typedef for half and half2

Change-Id: Ic844fa31b64a0354484b418df71869c2807200cc

include/hip/hcc_detail/hip_fp16.h

@@ -36,6 +36,9 @@ typedef struct __attribute__((aligned(4))){
   };
 } __half2;
 
+typedef __half half;
+typedef __half2 half2;
+
 /*
 Half Arithmetic Functions
 */