[llvm] [AArch64] Add ISel for postindex ld1/st1 in big-endian (PR #144387)

[John Brawn via llvm-commits]

john-brawn-arm wrote:

This broke buildbots that build with -Werror, fix in https://github.com/llvm/llvm-project/pull/144749

https://github.com/llvm/llvm-project/pull/144387