Further changes for Neon vector shuffles:

- change isShuffleMaskLegal to show that all shuffles with 32-bit and 64-bit
  elements are legal
- the Neon shuffle instructions do not support 64-bit elements, but we were
  not checking for that before lowering shuffles to use them
- remove some 64-bit element vduplane patterns that are no longer needed

llvm-svn: 105586