systemc: Implement sc_get_curr_process_handle().

The implementation is fairly trivial, but the pieces it relies on
weren't always available.

Change-Id: Ie77168ff336febd3ebe22c400f2b1f133e43aca7
Reviewed-on: https://gem5-review.googlesource.com/c/12973
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
1 file changed