ipa: place comment "IPA Multiplex" on ipa allocated msgbs

libosmocore offers the ipa API as general IPA Multiplex, which is e.g. used for
GSUP in osmo-msc. Looking at talloc reports, it is confusing to see "Abis/IP"
as msgb comment, because osmo-msc does not have an Abis interface.

Rename to "IPA Multiplex" as a more general description.

Change-Id: I3714dd21707bec0c4bcd0871e6ee8ff32d56b125
diff --git a/src/gsm/ipa.c b/src/gsm/ipa.c
index bc84850..fef73c3 100644
--- a/src/gsm/ipa.c
+++ b/src/gsm/ipa.c
@@ -582,7 +582,7 @@
 
 	headroom += sizeof(struct ipaccess_head);
 
-	nmsg = msgb_alloc_headroom(1200 + headroom, headroom, "Abis/IP");
+	nmsg = msgb_alloc_headroom(1200 + headroom, headroom, "IPA Multiplex");
 	if (!nmsg)
 		return NULL;
 	return nmsg;