Updated hip_porting_guide.md
Updated hip_porting_guide.md

Change-Id: Iaf32033597513aa2cbfde267487af35317ac67fe

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