dev: Scrub out some lingering uses of MemObject.

MemObject doesn't do anything any more, and is basically just an alias
for ClockedObject.

Change-Id: Ic0e1658609e4e1d7f4b829fbc421f222e4869dee
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20719
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

python: Don't assume SimObjects live in the global namespace

The importer in Python 3 doesn't like the way we import SimObjects
from the global namespace. Convert the existing SimObject declarations
to import from m5.objects. As a side-effect, this makes these files
consistent with configuration files.

Change-Id: I11153502b430822130722839e1fa767b82a027aa
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15981
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

learning_gem5: Adds the simple MemObject code

Adding more code from Learning gem5 Part II

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

Change-Id: Iaa9480c5cdbe4090364f02e81dc1d0a0ddac392a
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/5022
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>