sctp: Correctly cleanup procfs entries upon failure.

This patch remove the proc fs entry which has been created if fail to
set up proc fs entry for the SCTP protocol.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>