ARM: Correct alignment of structs passed as byval pointer

When a struct has bitfields overlapping with other members
(as required by the AAPCS), clang uses a packed struct to
represent this. If such a struct is large enough for clang to
pass it as a byval pointer (>64 bytes), we need to set the
alignment of the argument to match the original type.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203660 91177308-0d34-0410-b5e6-96231b3b80d8