Correct ill-formed merge in earlier commit and adjust for differences with the new CUDA natural indexing mechanism.

hipamd/include/hip/hcc_detail/hip_runtime.h

@@ -389,9 +389,18 @@ template<typename std::common_type<
 class Coordinates {
     using R = decltype(f(0));
 
-    struct X { __device__ operator R() const { return f(0); } };
-    struct Y { __device__ operator R() const { return f(1); } };
-    struct Z { __device__ operator R() const { return f(2); } };
+    struct X {
+        __device__ operator R() const { return f(0); }
+        __host__ operator R() const { return R{}; }
+    };
+    struct Y {
+        __device__ operator R() const { return f(1); }
+        __host__ operator R() const { return R{}; }
+    };
+    struct Z {
+        __device__ operator R() const { return f(2); }
+        __host__ operator R() const { return R{}; }
+    };
 public:
     static constexpr X x{};
     static constexpr Y y{};