Debug Info: Remove special-casing of indirect function argument handling.

LLVM has changed the semantics of dbg.declare for describing function
arguments. After this patch a dbg.declare always takes the *address*
of a variable as the first argument, even if the argument is not an
alloca.

https://bugs.llvm.org/show_bug.cgi?id=32382
rdar://problem/31205000

llvm-svn: 300523