mem-garnet: Fix garnet network interface stats

mem-garnet: Fix garnet network interface stats

Fixing a bug in garnet network interface where flit source delay is
computed using both tick and cycle.

Change-Id: If21a985f371a818611d13e9cd5ce344dbcf5fb2b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36416
Reviewed-by: Srikant Bharadwaj <srikant.bharadwaj@amd.com>
Maintainer: Matthew Poremba <matthew.poremba@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/37115
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jieming Yin <bjm419@gmail.com>