llvmpipe: do not enable tessellation shader without llvm coroutines support
Tessellation shader in llvmpipe depends on llvm coroutines support. So do not advertise tessellation shader support in llvmpipe if GALLIVM_HAVE_CORO is FALSE.
This fixes assertion in LLVMTokenTypeInContext() running tessellation shader tests with llvm version < 6.
Fixes: eb522717 "llvmpipe: add support for tessellation shaders"
Edited by Charmaine Lee