mem: Standardize mem folder header guards

Standardize all header guards in the mem directory according to the most
frequent patterns. In general they have the form:
mem: __FOLDER_TREE_FILE_NAME_HH__
ruby: __FOLDER_TREE_FILENAME_HH__

Change-Id: I983853e292deb302becf151bf0e970057dc24774
Reviewed-on: https://gem5-review.googlesource.com/7881
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-garnet: Fix garnet stats

This patch fix some statistics that in presence of a resetStats
instruction were not reseted. This bug makes impossible to obtain
reliable network statistics when the simulation doesn't start from tick
zero.

Change-Id: Ibec45f08d95bf0a533d94b70ec960719206ae945
Maintainer: Tushar Krishna <tushar@ece.gatech.edu>
Reviewed-on: https://gem5-review.googlesource.com/3700
Reviewed-by: Jieming Yin <bjm419@gmail.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

ruby: garnet2.0
Revamped version of garnet with more optimized single-cycle routers,
more configurability, and cleaner code.