systemc: Implement the sc_in class.
systemc: Implement the sc_in class.

Change-Id: I08174462cb650c7918a4e8f5284d4ee814cf595d
Reviewed-on: https://gem5-review.googlesource.com/12085
Reviewed-by: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>

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