ARM: correctly expand LDR-lit based globals.

Quite a major error here: the expansions for the Pseudos with and without
folded load were mixed up. Fortunately it only affects ARM-mode, when not using
movw/movt, on Darwin. I'm guessing no-one actually uses that combination.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223986 91177308-0d34-0410-b5e6-96231b3b80d8