[HIP] Fix return type in __clang_hip_cmath.h

Before, some functions like std::isgreater(double, doulbe) would return
a double instead of a bool.

Author: jmmartinez

clang/lib/Headers/__clang_hip_cmath.h

@@ -464,12 +464,13 @@ class __promote : public __promote_imp<_A1, _A2, _A3> {};
 #if __cplusplus >= 201103L
 #define __HIP_OVERLOAD2(__retty, __fn)                                         \
   template <typename __T1, typename __T2>                                      \
-  __DEVICE__ __CONSTEXPR__ typename __hip_enable_if<                           \
-      __hip::is_arithmetic<__T1>::value && __hip::is_arithmetic<__T2>::value,  \
-      typename __hip::__promote<__T1, __T2>::type>::type                       \
-  __fn(__T1 __x, __T2 __y) {                                                   \
-    typedef typename __hip::__promote<__T1, __T2>::type __result_type;         \
-    return __fn((__result_type)__x, (__result_type)__y);                       \
+  __DEVICE__ __CONSTEXPR__                                                     \
+      typename __hip_enable_if<__hip::is_arithmetic<__T1>::value &&            \
+                                   __hip::is_arithmetic<__T2>::value,          \
+                               __retty>::type                                  \
+      __fn(__T1 __x, __T2 __y) {                                               \
+    typedef typename __hip::__promote<__T1, __T2>::type __arg_type;            \
+    return __fn((__arg_type)__x, (__arg_type)__y);                             \
   }
 #else
 #define __HIP_OVERLOAD2(__retty, __fn)                                         \