Fix cast of __half for HIP-clang (#1475)

hipamd/include/hip/hcc_detail/hip_fp16.h

@@ -223,6 +223,7 @@ THE SOFTWARE.
                     Enable_if_t<
                         std::is_floating_point<T>{} &&
                         !std::is_same<T, double>{}>* = nullptr>
+                __host__ __device__
                 operator T() const { return data; }
             #endif
             __host__ __device__

hipamd/tests/src/deviceLib/hipTestHalf.cpp

@@ -30,6 +30,11 @@ THE SOFTWARE.
 
 #if __HIP_ARCH_GFX803__ || __HIP_ARCH_GFX900__ || __HIP_ARCH_GFX906__ || __HIP_ARCH_GFX908__
 
+__device__ void test_convert() {
+  __half x;
+  float y = (float)x;
+}
+
 __global__
 void __halfMath(bool* result, __half a) {
   result[0] = __heq(__hadd(a, __half{1}), __half{2});