update npu drivers to 6.4.2.1#28

Merged

numbqq merged 5 commits intokhadas:khadas-vims-4.9.yfrom

yan-wyb:khadas-vims-4.9.y

Sep 23, 2020

Commits on Aug 31, 2020

Merge pull request #2 from khadas/khadas-vims-4.9.y
yan-wyb
authored

Commits on Sep 19, 2020

Merge pull request #3 from khadas/khadas-vims-4.9.y
yan-wyb
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Commits on Sep 22, 2020