ARM: PCS non-compliance when struct is padded to avoid register/stack split, and requires internal padding

When we were padding a struct to avoid splitting it between registers and
the stack, we were throwing away the type which the argument should be coerced
to.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209122 91177308-0d34-0410-b5e6-96231b3b80d8