add rvv support for lstm operator

[chenglimin]

test passed at Musepi, BananaPi and K230.

[tencent-adm]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ chenglimin
❌ nihui
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[nihui]

You created the pull request with the wrong branch.