sctp: translate network order to host order when users get a hmacid

Commit ed5a377d ("sctp: translate host order to network order when
setting a hmacid") corrected the hmacid byte-order when setting a hmacid.
but the same issue also exists on getting a hmacid.

We fix it by changing hmacids to host order when users get them with
getsockopt.

Fixes: Commit ed5a377d ("sctp: translate host order to network order when setting a hmacid")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>