Revert r324903 "[AArch64] Refactor identification of SIMD immediates"
Revert r324903 "[AArch64] Refactor identification of SIMD immediates"

It caused "Cannot select: t33: f64 = AArch64ISD::FMOV Constant:i32<0>"
in Chromium builds. See PR36369.

> Get rid of icky goto loops and make the code easier to maintain (NFC).
>
> Differential revision: https://reviews.llvm.org/D42723

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@325034 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm