[submodule] now use a feature branch of VTR as a submodule

.gitmodules

@@ -6,3 +6,7 @@
 [submodule "yosys-plugins"]
 	path = yosys-plugins
 	url = https://github.com/SymbiFlow/yosys-symbiflow-plugins
+[submodule "vtr-verilog-to-routing"]
+	path = vtr-verilog-to-routing
+	url = https://github.com/verilog-to-routing/vtr-verilog-to-routing.git
+    branch = openfpga

vtr-verilog-to-routing

@@ -0,0 +1 @@
+Subproject commit 04161e5144c7c4fd2ecf980aff021ad980d3e6eb