[InstCombine] foldICmpWithLowBitMaskedVal(): 'icmp sgt/sle': avoid miscompiles

A precondition 'x != 0' was forgotten by me:
https://rise4fun.com/Alive/JFNP
https://rise4fun.com/Alive/jHvL

These 4 folds with non-constants could be re-enabled,
but for now let's go for the simplest solution.

https://bugs.llvm.org/show_bug.cgi?id=42198

llvm-svn: 362911