network: basic link bw for garnet and simple networks

network: basic link bw for garnet and simple networks

This patch ensures that both Garnet and the simple networks use the bw value
specified in the topology.  To do so, the patch generalizes the specification
of bw for basic links.  This value is then translated to the specific value
used by the simple and Garnet networks.  Since Garent does not support
non-uniformed link bandwidth, the patch also adds a check to ensure all bws are
equal.

--HG--
rename : src/mem/ruby/network/BasicLink.cc => src/mem/ruby/network/simple/SimpleLink.cc
rename : src/mem/ruby/network/BasicLink.hh => src/mem/ruby/network/simple/SimpleLink.hh
rename : src/mem/ruby/network/BasicLink.py => src/mem/ruby/network/simple/SimpleLink.py