The code in sctp_getsockopt_maxburst() doesn't allow len to be larger
then struct sctp_assoc_value, which is a common case where app writers
just pass down the sizeof(buf) or something similar.

This patch fix the problem.
Signed-off-by: NWei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: NVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>