ARM64: remove holes from *all* HFAs on the stack.

My first attempt to make sure HFAs were contiguous was in the block dealing
with padding registers, which meant it only triggered on the first stack-based
HFA. This should extend it to the rest as well.

Another part of PR19432.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206456 91177308-0d34-0410-b5e6-96231b3b80d8