[llvm] [AArch64][ARM] Avoid some APFloat copies in tablegen patterns. NFC. (PR #114416)

[David Green via llvm-commits]

https://github.com/davemgreen approved this pull request.

If you feel like capitalising Enc that would be an improvement too. Either way LGTM, cheers.

https://github.com/llvm/llvm-project/pull/114416