[InstCombine] Fix PR37526: MinMax patterns produce an infinite loop.

Summary:
This patch fixes PR37526 by simplifying the newly generated LoadInst
instructions. If the pointer address is a bitcast from the pointer to
the NewType, we can just remove this extra bitcast instead of creating
the new one. This fixes the PR37526 + may speed up the whole compilation
process.

Reviewers: spatel, RKSimon, hfinkel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D47144

llvm-svn: 332855