stdlib: Move 'connect_things' to AbstractBoard constructor

This patch moves 'connect_things' to the AbstractBoard constructor,
thereby meaning it does not need to be called directly in gem5
configuration scripts. This method has been changed to private as a
result.

As boards that inherit from AbstractBoard require certain things to be
setup prior to `connect_things` being called, a new abstract function,
`_setup_board` has been created. This is called in the AbstractBoard
constructor before `connect_things` and can be overridden by boards to
setup board properties as required.

Change-Id: I558a4321b850a6b19e20b7d56d0bcae5805114b6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52184
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
15 files changed