mem-garnet: Add a garnet namespace

Add a namespace encapsulating all garnet files.

GarnetSyntheticTraffic, from
cpu/testers/garnet_synthetic_traffic/GarnetSyntheticTraffic.hh
has not been added to this namespace.

Change-Id: I5304ad3130100ba325e35e20883ee9286f51a75a
Issued-on: https://gem5.atlassian.net/browse/GEM5-987
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47306
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Srikant Bharadwaj <srikant.bharadwaj@amd.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Srikant Bharadwaj <srikant.bharadwaj@amd.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
36 files changed