uboot-imx

ar8031: modify the config func of ar8031 to ar8021_config

ar8031 has the same config steps with ar8021, so change its
config func to ar8021_config instead of genphy_config.

Signed-off-by: Zhao Qiang <B45475@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>