[llvm] [ARM][NEON] Add constraint to vld2 Odd/Even Pseudo instructions. (PR #79287)

[Alfie Richards via llvm-commits]

AlfieRichardsArm wrote:

I believe only the odd variants have the WB variant as it is constraining the input register which is the same for both, so only one constraint is needed.

https://github.com/llvm/llvm-project/pull/79287