ran_peer.c is not the proper place to parse messages, because it should be RAN
agnostic. All parsing and encoding belongs in ran_msg_a.c and ran_msg_iu.c.
Move the Osmux TLV parsing into the is_reset_msg op: add supports_osmux
out-parameter (and add a logging fi pointer). To be able to modify msg->l3h,
also make the msgb arg non-const.
In ranap_is_reset_msg(), always return non-support for Osmux.
In bssmap_is_reset_msg(), return 0 if no TLVs were parsed, 1/-1 if an Osmux TLV
was present/not present.
Update the osmux support flag directly where the ConnectionLess message is
received, so that there is only one place responsible for that.
Related: OS#4595
Change-Id: I1ad4a3f9356216dd4bf8c48fba29fd23438810a7
b697274daa