Add License notes for CUDA Half Precision headers

LICENSES.third-party

@@ -491,3 +491,17 @@ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+CUDA Half Precision Headers
+---------------------------
+
+The files numba/cuda/cuda_fp16.h and numba/cuda/cuda_fp16.hpp are vendored from
+the CUDA Toolkit version 11.2.2 under the terms of the NVIDIA Software License
+Agreement and CUDA Supplement to Software License Agreement, available at:
+
+https://docs.nvidia.com/cuda/archive/11.2.2/eula/index.html
+
+These files are distributable as listed in Attachment A:
+
+https://docs.nvidia.com/cuda/archive/11.2.2/eula/index.html#attachment-a