[LoopCacheAnalysis] Drop isLoopSimplifyForm check (NFCI) (#204822)
This patch removes the isLoopSimplifyForm() check from
LoopCacheAnalysis. This check was problematic when I tried migrating
LoopCachePrinterPass from a loop pass to a function pass (i.e.,
#204807), because the former applies the loop-simplify pass via
FunctionToLoopPassAdapter, whereas the latter does not. I believe this
check is meaningless because the analysis doesn't pay attention to the
details of the actual loop structure. So this change should not affect
the behavior of the pass.