I have found the reason and solved.
emac_port_mode[0] has PLATFORM_EMAC_PORT_MODE_AMC.
Overwrite the value to PLATFORM_EMAC_PORT_MODE_PHY for MAC0 interface.
client.c
extern PLATFORM_EMAC_PORT_MODE emac_port_mode[PLATFORM_MAX_EMAC_PORT_NUM];
emac_port_mode[0] = PLATFORM_EMAC_PORT_MODE_PHY;
Thank to CHAO HU.
http://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/t/226969.aspx