spi: fsl-lpspi: Add imx8ulp compatible string

The lpspi on i.MX8ULP is derived from i.MX7ULP, it uses two
compatible strings, so update the comaptible string for i.MX8ULP.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211120113454.785997-4-peng.fan@oss.nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>