[NFC][Reassociate] Delay checking isLoadCombineCandidate() until after...

[NFC][Reassociate] Delay checking isLoadCombineCandidate() until after ShouldConvertOrWithNoCommonBitsToAdd() but before haveNoCommonBitsSet()

This appears to improve -O3 compile-time performance somewhat:
https://llvm-compile-time-tracker.com/compare.php?from=87369c626114ae17f4c637635c119e6de0856a9a&to=c04b8271e1609b0dfb20609b40844b0c4324517e&stat=instructions
It doesn't look like delaying it until after haveNoCommonBitsSet() is better:
https://llvm-compile-time-tracker.com/compare.php?from=c04b8271e1609b0dfb20609b40844b0c4324517e&to=b2943d450eaf41b5f76d2dc7350f0a279f64cd99&stat=instructions