sctp: add sockopt SCTP_ENABLE_STREAM_RESET

This patch is to add sockopt SCTP_ENABLE_STREAM_RESET to get/set
strreset_enable to indicate which reconf request type it supports,
which is described in rfc6525 section 6.3.1.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -1257,6 +1257,8 @@ struct sctp_endpoint {
 	__u8  auth_enable:1,
 	      prsctp_enable:1,
 	      reconf_enable:1;
+
+	__u8  strreset_enable;
 };
 
 /* Recover the outter endpoint structure. */
@@ -1872,6 +1874,8 @@ struct sctp_association {
 	     prsctp_enable:1,
 	     reconf_enable:1;
 
+	__u8 strreset_enable;
+
 	__u32 strreset_outseq; /* Update after receiving response */
 	__u32 strreset_inseq; /* Update after receiving request */