The downstream copy of SwiftShader in AOSP has license info changes:
https://android-review.googlesource.com/c/platform/external/swiftshader/+/1576044
This change cherry picks it into the upstream repo.

Also add natsu@ and schuffelen@ to OWNERS to retain their privileges
when we directly roll SwiftShader into AOSP.

Bug: skia:11901
Change-Id: Ibfba7640d0133740c38fc0f00d32fcb5e11f8a11
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/54148
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Commit-Queue: Nicolas Capens <nicolascapens@google.com>