spi: fsl_dspi: add new compatible fsl, ls1021a-v1.0-dspi

spi: fsl_dspi: add new compatible fsl, ls1021a-v1.0-dspi

The official ls1028a binding of the driver uses the following as
compatibles:
  compatible = "fsl,ls1028a-dspi", "fsl,ls1021a-v1.0-dspi";

Add the missing compatible to the driver and update the device tree.
We can use the fallback "fsl,ls1021a-v1.0-dspi", because the endianness
is determined by the little-endian property and not by the compatible
string itself. Further, we won't need and specific details on the DMA
configuration (which is different on the LS1021A). If it's ever needed,
we can later add the more specific "fsl,ls1028a-dspi" compatible to the
driver.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>