I tried to build usb/gadget/file_storage.c (CONFIG_USB_FILE_STORAGE=y),
but it uses "handle_exception()" for its own purposes, which conflicts
with the ia64 definition.  ia64 only uses handle_exception() within
arch code, so it seems like we ought to rename it to be ia64-specific.
done_with_exception() looks similar, so I renamed it as well, although
there's no actual conflict.