[ARM] Update ReconstructShuffle to handle mismatched types

Summary:
Port the ReconstructShuffle function from AArch64 to ARM
to handle mismatched incoming types in the BUILD_VECTOR
node.

This fixes an outstanding FIXME in the ReconstructShuffle
code.

Reviewers: t.p.northover, rengolin

Subscribers: aemerson, llvm-commits, rengolin

Differential Revision: http://reviews.llvm.org/D11720

llvm-svn: 244314