New get_rr_node_indices doesn't swap X/Y for CHANX

[litghost]

See https://github.com/verilog-to-routing/vtr-verilog-to-routing/blob/master/vpr/src/route/rr_graph2.cpp#L1288-L1291, which is missing from https://github.com/verilog-to-routing/vtr-verilog-to-routing/blob/master/vpr/src/route/rr_graph2.cpp#L1227

[litghost]

@kmurray I think this is you?

[kmurray]

Yep, thanks for the catch! I'll fix that.

That RR node indicies requires that is generally very error prone, which is why we eventually want to fix it (see #355)