Make __gnu_h2f_ieee and __gnu_f2h_ieee visible
Make __gnu_h2f_ieee and __gnu_f2h_ieee visible

Make __gnu_h2f_ieee and __gnu_f2h_ieee visible so that hipTestHalf
test can succeed in Clang compiler + Hcc RT.

Change-Id: I5f7d5db19e559b3b66356f0170a8dbc1e5505f3e

ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP