[llvm] [DAG] SDPatternMatch - Fix m_Reassociatable mismatching (PR #170061)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

collectLeaves can technically collect too many nested leaves - so we'd need to do some kind of bound check.

In the meantime I can split the m_ReassociatableAdd / m_ReassociatableAnd pairs in #169644

https://github.com/llvm/llvm-project/pull/170061