[llvm] [AArch64] Keep floating-point conversion in SIMD (PR #147707)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

For now I've pushed a commit to remove the problematic code, I forgot the extracts are not as flexible as you'd hope.  The majority of the PR's functionality is maintained and we can circle back if supporting the post inc store case proves valuable.

https://github.com/llvm/llvm-project/pull/147707