Added preservation of interconnect mux inputs

Signed-off-by: Maciej Kurc <mkurc@antmicro.com>

tests/vtr/lutff-pair/golden.pb_type.xml

diff --git a/tests/vtr/lutff-pair/golden.pb_type.xml b/tests/vtr/lutff-pair/golden.pb_type.xml
index 2d667bf..ea403db 100644
--- a/tests/vtr/lutff-pair/golden.pb_type.xml
+++ b/tests/vtr/lutff-pair/golden.pb_type.xml
@@ -39,16 +39,16 @@
       <port from="lut" name="I[3]" type="output"/>
     </direct>
     <mux name="mux">
-      <port from="lut" name="O" type="input">
-        <metadata>
-          <meta name="fasm_mux">L</meta>
-        </metadata>
-      </port>
       <port from="ff" name="Q" type="input">
         <metadata>
           <meta name="fasm_mux">F</meta>
         </metadata>
       </port>
+      <port from="lut" name="O" type="input">
+        <metadata>
+          <meta name="fasm_mux">L</meta>
+        </metadata>
+      </port>
       <port name="O" type="output"/>
       <metadata>
         <meta name="type">bel</meta>

v2x/vlog_to_pbtype.py

diff --git a/v2x/vlog_to_pbtype.py b/v2x/vlog_to_pbtype.py
index 8c4f8c7..e0a0e66 100755
--- a/v2x/vlog_to_pbtype.py
+++ b/v2x/vlog_to_pbtype.py
@@ -268,10 +268,14 @@
 ) -> ET.Element:
 
     mux_xml = ET.SubElement(ic_xml, "mux", {"name": mux_name})
-    for mux_input, driver in mux_inputs.items():
+
+    keys = sorted(list(mux_inputs.keys()))
+    for mux_input, driver in [(k, mux_inputs[k],) for k in keys]:
         create_port(mux_xml, driver, "input", metadata={'fasm_mux': mux_input})
+
     assert len(mux_outputs) == 1, mux_outputs
-    for mux_pin, sinks in mux_outputs.items():
+    keys = sorted(list(mux_outputs.keys()))
+    for mux_pin, sinks in [(k, mux_outputs[k],) for k in keys]:
         assert len(sinks) == 1, sinks
         for sink_pin, path_attr in sinks:
             create_port(mux_xml, sink_pin, "output")