systemc: Track the module who's end_of_elaboration callback we're in.
systemc: Track the module who's end_of_elaboration callback we're in.

Change-Id: Ib5fe3232cfea26df0c3396c583fd80da429cbdd5
Reviewed-on: https://gem5-review.googlesource.com/c/12442
Reviewed-by: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>

TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu