rds_ib/iw: fixed big endianness conversion issue for dp->dp_ack_seq

rds_ib/iw: fixed big endianness conversion issue for dp->dp_ack_seq

dp->dp_ack_seq is used in big endian format. We need to do the
big endianness conversion when we assign a value in host format
to it.

(This patch is ported from UEK2)

Orabug: 21684819

Acked-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Reviewed-by: Wengang Wang <wen.gang.wang@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: Qing Huang <qing.huang@oracle.com>
Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>