Add compatability matrix for parboil

hpvm/test/parboil/README.md

+# Current Benchmark Compatability
+
+| Benchmark | Version | Supported on CPU | Supported on GPU |
+| :-------- | :------ | :--------------: | :--------------: |
+| sgemm     | visc    | ✔                | ✔                |
+| stencil   | visc    | ✔                | ✔                |
+| spmv      | visc    | ✔                | ✘                |
+| lbm       | visc    | ✔                | ✘                |