This corresponds to change-id If5099e60681a215e798b6675f21813f26769c253 in
libosmocore, which is now required to build openbsc.
Related: OS#1592
Change-Id: I2f06aaa6eb54eafa860cfed8e72e41d82ff1c4cf
In general, if a function generates output data like a msgb (or in this
case filling an osmo_oap_message structure), the output argument
precedes the source. This is what we use all over libosmo*, and it is
modelled after memcpy(), where dst is the first argument, before src.
Let's align osmo_oap_decode(). Intestingly, osmo_oap_encode was already
correct, so the encode/decode functions used different conventions
before.