[crypto] add non-blocking rsa_3072_verify function

[timothytrippel]

Previously, only a blocking version of the rsa_3072_verify function existed.

For the power virus test (see #14814), however, we want the ability to initiate OTBN operations, and then free up the CPU to complete other tasks.

This adds a non-blocking version of the rsa_3072_verify function to the crypto library to support this use case.

Signed-off-by: Timothy Trippel [email protected]

[timothytrippel]

@jadephilipoom (as discussed offline):

As part of the power virus test I want to activate the OTBN by doing an RSA computation, but I came across an issue: the current rsa_3072_verify function blocks. What I would like to do, is kick off OTBN RSA operations, and free up the CPU to do other tasks, then come back and check the result later. I saw your comment about this here, and went ahead an implemented a non-blocking version of the function in this PR. I used the terms "async/await" borrowed from JS land. However if you had separate plans for the API, please feel free to suggest an alternative or close the PR, I just wanted to put together example of what I was looking for.

[jadephilipoom]

Thanks, Tim! For the cryptolib API we've been using start and finalize terminology instead of async and await; would you mind changing the names just so that it's uniform? Otherwise this looks great 🙂

[timothytrippel]

Sounds good, fixed. Thanks!