dlm: remove duplicated include from lowcomms.c

Remove duplicated include.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -52,7 +52,6 @@
 #include <linux/mutex.h>
 #include <linux/sctp.h>
 #include <linux/slab.h>
-#include <linux/sctp.h>
 #include <net/sctp/sctp.h>
 #include <net/ipv6.h>