spi: spi-fsl-dspi: Support SPI software timestamping in all non-DMA modes

There's no reason to keep this .ptp_sts_supported property explicitly in
devtype_data, since it can be deduced from the operating mode alone.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Message-Id: <20200302001958.11105-6-olteanv@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>