panfrost: Add some WRITE_VALUE tests for Bifrost
Right now, the main submit tests (which are equivalent to glClear() ) don't yet work on Bifrost. In the mean time to sanity check things, let's add some even simpler tests uses WRITE_VALUE (as of bifrost, a fully generic dword write primitive, which is barely used in GL/CL/VK but makes for nice igt tests).
These tests pass, so at least something is awake.