[llvm] [SelectionDAG] Correct the implementation of m_AllOnes. (PR #90776)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

@AtariDreams SDPatternMatch was added after the 18.x release branch (5874874c24720dc24fde12327f81369ef4af4e0b) - https://github.com/llvm/llvm-project/tree/release/18.x/llvm/include/llvm/CodeGen - this bugfix is not relevant to 18.x

https://github.com/llvm/llvm-project/pull/90776