software/ors-amarisoft: ru/lopcomm: Simplify and clarify cu_config.jinja2.xml

We can use mathematical relation in between ports, channels and tx/rx endpoints
to bring structure and clarity in RU setup.

Also, while on it, document how tx/rx data flow are organized as it was not
clear just from reading ORAN specs and I had to deduce it.

/cc @jhuge, @lu.xu, @xavier_thompson, @Daetalus
/reviewed-by @lu.xu
/reviewed-on nexedi/slapos!1468

software/ors-amarisoft/buildout.hash.cfg

@@ -136,7 +136,7 @@ md5sum = e435990eb0a0d4be41efa9bd16dce09b
 
 [ru_lopcomm_cu_config.jinja2.xml]
 _update_hash_filename_ = ru/lopcomm/cu_config.jinja2.xml
-md5sum = d10b063ad4edc760e154f7a8d63bea47
+md5sum = 09123ad68c6d8e7e4e201bcc2ab331c6
 
 [software.cfg.html]
 _update_hash_filename_ = gadget/software.cfg.html