[NFC]: Fix PVS Studio warning in LoopNestAnalysis

Summary:This patch fixes the following warnings uncovered by PVS
Studio:

/home/xbolva00/LLVM/llvm-project/llvm/lib/Analysis/LoopCacheAnalysis.cpp
353 warn V612 An unconditional 'return' within a loop.
/home/xbolva00/LLVM/llvm-project/llvm/lib/Analysis/LoopCacheAnalysis.cpp
456 err V502 Perhaps the '?:' operator works in a different way than it
was expected. The '?:' operator has a lower priority than the '=='
operator.
Authored By:etiotto
Reviewer:Meinersbur, kbarton, bmahjour, Whitney, xbolva00
Reviewed By:xbolva00
Subscribers:hiraditya, llvm-commits
Tag:LLVM
Differential Revision:https://reviews.llvm.org/D69821