Revert "[ARM] Combine base-updating/post-incrementing vector load/stores."

Revert "[ARM] Combine base-updating/post-incrementing vector load/stores."

This reverts commit r223862, as it created a regression on the test-suite
on test MultiSource/Benchmarks/Ptrdist/anagram by scrambling the order
in which the words are shown. We'll investigate the issue and re-apply
when safe.

llvm-svn: 224198