配置AXI slave VIP，使其能接受两个outstanding transfer

To enable the outstanding burst of slave AXI VIP, please set dw_vip_axi_port_configuration::m_nNumOutstandingXact = n, then the Slave can response ARREADY earlier without waiting for the end of previous burst.
for example:

dw_vip_axi_system_model_configuration vip_axi_sys_cfg;
dw_vip_axi_port_model_configuration   vip_axi_slave_cfg;

vip_axi_sys_cfg = new (, 1, 1, VMT_BOOLEAN_FALSE);

/* Do system level configuration */
vip_axi_sys_cfg.m_enAddrWidth = dw_vip_axi_configuration :: ADDR_BUS_WIDTH_32;
vip_axi_sys_cfg.m_enDataWidth = dw_vip_axi_configuration :: DATA_BUS_WIDTH_64;

/* Configure this member to maximum ID width within all masters in the system */
vip_axi_sys_cfg.m_nMstrIdWidth = 4;

/* !!!!!!!!!  Create port model configuration object for VIP slave. */
vip_axi_slave_cfg = vip_axi_sys_cfg.createPortMdlCfg (`DW_VIP_AXI_SLAVE_PORT_CFG, 0);

/* !!!!!!!!!  Do port level configuration */
vip_axi_slave_cfg.m_oPortCfg.m_nNumOutstandingXact = 2;// 2 outstanding burst

vip_axi_slave_cfg.m_oPortCfg.m_nIdWidth = 4;
vip_axi_slave_cfg.m_oPortCfg.m_enMemoryDefaultPattern  = dw_vip_axi_configuration::PATTERN_INCR;