systemc: Implement the sc_*_resolved classes.

Change-Id: Ib595da10e0f900ee4cc1847d41d29251dacb55d7
Reviewed-on: https://gem5-review.googlesource.com/c/12620
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Stub out the predefined channels.

Change-Id: Ie030aad26875bd49e54981ec1e9076b7b5af6630
Reviewed-on: https://gem5-review.googlesource.com/10839
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>