spi: spi-fsl-dspi: Use specific compatible strings for all SoC instantiations

Currently, the device tree bindings submitted in mainline for Layerscape
SoCs look like this:

LS1021A:
compatible = "fsl,ls1021a-v1.0-dspi";

LS1012A:
compatible = "fsl,ls1012a-dspi", "fsl,ls1021a-v1.0-dspi";

LS2085A:
compatible = "fsl,ls2085a-dspi";

LS2088A:
compatible = "fsl,ls2080a-dspi", "fsl,ls2085a-dspi";

LX2160A:
compatible = "fsl,lx2160a-dspi", "fsl,ls2085a-dspi";

LS1043A:
compatible = "fsl,ls1043a-dspi", "fsl,ls1021a-v1.0-dspi";

LS1046A:
compatible = "fsl,ls1021a-v1.0-dspi";

Due to a lack of a more specific compatible string, LS1012A, LS1043A and
LS1046A will fall under the LS1021A umbrella, and LS2088A and LX2160A
under the LS2085A umbrella.

They do work in those modes, but there are slight differences in the
hardware instantiations, mostly related to FIFO sizes (with the more
specific compatible strings, the FIFO size can be increased properly).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Message-Id: <20200302001958.11105-3-olteanv@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>