[InstSimplify] simplifyUnsignedRangeCheck(): handle few tautological cases (PR43251)

[InstSimplify] simplifyUnsignedRangeCheck(): handle few tautological cases (PR43251)

Summary:
This is split off from D67356, since these cases produce a constant,
no real need to keep them in instcombine.

Alive proofs:
https://rise4fun.com/Alive/u7Fk
https://rise4fun.com/Alive/4lV

https://bugs.llvm.org/show_bug.cgi?id=43251

Reviewers: spatel, nikic, xbolva00

Reviewed By: spatel

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67498

llvm-svn: 371921