[AArch64] CondOpt pass is missing FCMP instructions when searching backward for
a CMP which defines the flags used by B.CC.

http://reviews.llvm.org/D6047
Patch by Zhaoshi Zheng <zhaoshiz@codeaurora.org>!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220961 91177308-0d34-0410-b5e6-96231b3b80d8