learning_gem5: Adding code for SimpleCache

This is the rest of the code for part 2.

See http://learning.gem5.org/book/part2/simplecache.html

Change-Id: I5db099266a1196914656be3858fdd5fb4f8eab48
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/5023
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
5 files changed