Fix previous commit: [FastISel][AArch64] Simplify XALU multiplies.

When folding the intrinsic flag into the branch or select we also have to
consider the fact if the intrinsic got simplified, because it changes the
flag we have to check for.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218034 91177308-0d34-0410-b5e6-96231b3b80d8