sctp: translate host order to network order when setting a hmacid

now sctp auth cannot work well when setting a hmacid manually, which
is caused by that we didn't use the network order for hmacid, so fix
it by adding the transformation in sctp_auth_ep_set_hmacs.

even we set hmacid with the network order in userspace, it still
can't work, because of this condition in sctp_auth_ep_set_hmacs():

		if (id > SCTP_AUTH_HMAC_ID_MAX)
			return -EOPNOTSUPP;

so this wasn't working before and thus it won't break compatibility.

Fixes: 65b07e5d ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>