Remove class abstraction from ARM struct byval lowering

This commit changes the struct byval lowering for arm to use inline
checks for the subtarget instead of a class abstraction to represent
the differences. The class abstraction was judged to be too much
code for this task.

No intended functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193357 91177308-0d34-0410-b5e6-96231b3b80d8