SCTP : Fix to process bundled ASCONF chunk correctly

If ASCONF chunk is bundled with other chunks as the first chunk, when
process the ASCONF parameters, full packet data will be process as the
parameters of the ASCONF chunk, not only the real parameters. So if you
send a ASCONF chunk bundled with other chunks, you will get an unexpect
result.
This problem also exists when ASCONF-ACK chunk is bundled with other chunks.

This patch fix this problem.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>