cmd/internal/obj/riscv: support zawrs assembly on riscv64

[newborn22]

This patch add support for Zawrs extension on RISCV64.

Updates #76179

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Message from Gopher Robot:

Patch Set 1:

(1 comment)

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Message from wh q:

Patch Set 1:

(1 comment)

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Message from Meng Zhuo:

Patch Set 2:

(4 comments)

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[gopherbot]

This PR (HEAD: 9039c3b) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/717920.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
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• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from wh q:

Patch Set 3:

(4 comments)

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Message from Meng Zhuo:

Patch Set 3:

(1 comment)

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Message from wh q:

Patch Set 3:

(1 comment)

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