[llvm] [AArch64] Disable consecutive store merging when Neon is unavailable (PR #111519)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm commented:

When I rewrite `consecutive_stores_quadruple_streaming_function` to use `llvm.vector.reduce.fadd` instead of the target specific intrinsic the problem goes away.  It's worth investigating to see if we're missing a useful combine or something before flicking the `canMergeStoresTo` switch.

https://github.com/llvm/llvm-project/pull/111519