systemc: Implement positional binding.

systemc: Implement positional binding.

Change-Id: Ifbcd7e4148b82b9bf5241e040e812925daea3705
Reviewed-on: https://gem5-review.googlesource.com/12263
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>