[clang] [CIR][AArch64] Upstream for vector vector shl (PR #191655)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space commented:

This is what I had in mind, thanks! I am posting some small suggestions to tweak this a bit.

https://github.com/llvm/llvm-project/pull/191655