select/cray: revert use of fake coordinates

This reverts the introduction of "fake" Y coordinates in order to disambiguate
nodes sharing the same Gemini network interface. Their introduction breaks
assumptions that may be present e.g. in scripts, and also it is no longer
easily possible to pair nodes sharing a Gemini chip for optimal performance.

Show the real coordinates instead, which is more transparent.
Patch from Gerrit Renker, CSCS.