ls102xa: ddr4: Use LPUART as console output to verify DCU driver

On QDS board with DDR4 DIMM, LPUART is used as console
output to verify DCU driver. This patch adds
ls1021aqds_ddr4_nor_lpuart_defconfig for this support.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>