TOS bits != DSCP

We have VTY options that allow to set the DSCP value.  However, we
then call a function to set the TOS bits in the kernel.  This is
very wrong.  The DSCP is only the upper 6 bits of the 8-bit TOS
value, and hence we are mussing that translation.

As libosmocore now has a helper function osmo_sock_set_dscp(),
let's make use of it and don't care about the low-level details.

However, this means we need to finally remove the deprecated
alias for "rtp ip-tos <0-255>".

Closes: OS#5137
Change-Id: I9c18c90273be97aedd2ad212b82f650e35c32851
Depends: libosmocore.git Ia4ba389a5b7e3e9d5f17a742a900d6fd68c08e40
diff --git a/doc/manuals/chapters/configuration.adoc b/doc/manuals/chapters/configuration.adoc
index 2e2772e..177c096 100644
--- a/doc/manuals/chapters/configuration.adoc
+++ b/doc/manuals/chapters/configuration.adoc
@@ -101,7 +101,7 @@
  rtp net-range 6000 6011
  rtp net-bind-ip 192.168.100.130
  rtp ip-probing
- rtp ip-tos 184
+ rtp ip-dscp 46
  no rtp keep-alive
  bind port 2428
  number endpoints 30