[llvm] [Hexagon] Add missing pattern for v8i1 type (PR #120703)

[Brian Cain via llvm-commits]

androm3da wrote:

> @androm3da This actually fixes #64970.

That one seems to resemble #59009.  I think this fix seems like an appropriate one but in the longer term we should be mindful of the issues Krzyzstof raised.  

Regarding this PR: LGTM but @iajbar or someone else should approve it.

https://github.com/llvm/llvm-project/pull/120703