Verify is the parsed data is at least the size of the struct, not
exactly the size. Make it accept messages with additional data, like
the SDP information the TTCN-3 testsuite is sending since
Ic9568c8927507e161aadfad1a4d20aa896d8ae30.
This change makes the size checks consistent with the two other size
checks in the file:
if (rc < sizeof(*rtp)) {
if (rc < sizeof(**mncc)) {
Related: OS#4282
Change-Id: I522ce7f206932a816a64f03d916799c3215bb8c7
Oliver Smith
b544ea396a