sim: kernelExtras optional load addresses

sim: kernelExtras optional load addresses

This patch provides a new "System" parameter named "kernel_extras_addrs".
This allows to optionally specify fixed load addresses for the
additional kernel objects. This is useful to load arbitrary blobs into
memory.

Change-Id: I4725763b86c29f72282d1c184d4284d90f9d3016
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23566
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>