configs: ls1028aqds: add lpuart config

Add lpuart config to enable lpuart feature.

Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
Signed-off-by: Yuantian Tang <andy.tang@nxp.com&gt;.>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>