dm: arm: ls1021a: Move to driver model for USB

This patch enables driver model for USB in defconfigs for LS1021A
platforms.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: York Sun <york.sun@nxp.com>