[InstCombine] foldICmpWithLowBitMaskedVal(): disable 2 faulty folds.

These two folds are invalid for this non-constant pattern
when the mask ends up being all-ones:
https://rise4fun.com/Alive/9au
https://rise4fun.com/Alive/UcQM

Fixes https://bugs.llvm.org/show_bug.cgi?id=39861

llvm-svn: 348181