bind gpu implementation to lowering.

src/targets/gpu/lowering.cpp

@@ -45,6 +45,7 @@
 #include <migraphx/gpu/pad.hpp>
 #include <migraphx/gpu/gather.hpp>
 #include <migraphx/gpu/lrn.hpp>
+#include <migraphx/gpu/fp_conversion.hpp>
 #include <utility>
 #include <functional>
 #include <algorithm>
@@ -101,6 +102,7 @@ struct miopen_apply
         add_extend_op<hip_logsoftmax, op::logsoftmax>("logsoftmax");
         add_extend_op<hip_gather, op::gather>("gather");
         add_extend_op<hip_pad, op::pad>("pad");
+        add_extend_op<hip_fp_conversion, op::fp_conversion>("fp_conversion");
 
         add_lrn_op();
         add_convolution_op();