dm: dts: ls1021a-twr: Enable DSPI2 on LS1021ATWR

Erratum A-008022 has been fixed on LS1021A Rev2.0.
So we can use DSPI2 now, this patch enable DSPI2
in dts for LS1021ATWR.

Signed-off-by: Yuan Yao <yao.yuan@freescale.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>