[Mesa-stable] Additional changes to include in mesa 21.0

[Ilia Mirkin]

Hi Dylan,

Please include the following changes in the 21.0 branch. If you're
making additional releases for 20.3, feel free to include them there
as well:

commit 55c42b7885701098cff9cc0fd0ffe08b0a90ea8b
Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Wed Jan 13 02:14:07 2021 -0500

    st/mesa: fix broken moves for u2i64 and related ops

commit 6638b58ccf17ce3a00a8ecbf5f39b5bedef238ed
Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Fri Jan 15 17:01:27 2021 -0500

    nv50/ir: clear dnz flag when converting mul/mad to simpler ops

Thanks,

  -ilia