Fix README for invalid command

`-DCMAKE_INSTALL_PATH` is not valid,use `-DCMAKE_INSTALL_PREFIX` instead

https://github.com/RadeonOpenCompute/ROCR-Runtime/pull/171/

Suggested-by: fjh1997 on github
Change-Id: Ibb85da7fe755b662fa9a836d6fbe3394d34a0337

runtime/hsa-runtime/README.md

@@ -79,7 +79,7 @@ ROCm packages installed, execute the following from `src/`:
 ```bash
 mkdir build
 cd build
-cmake -DCMAKE_INSTALL_PATH=/opt/rocm ..
+cmake -DCMAKE_INSTALL_PREFIX=/opt/rocm ..
 make
 make install
 make package