spi: introduce SPI_MODE_X_MASK macro

Provide a macro to filter all SPI_MODE_0,1,2,3 mode in one run.

The latest SPI framework will parse the devicetree in following call
sequence: of_register_spi_device() -> of_spi_parse_dt()
So, driver do not need to pars the devicetree and will get prepared
flags in the probe.

On one hand it is good far most drivers. On other hand some drivers need to
filter flags provide by SPI framework and apply know to work flags. This drivers
may use SPI_MODE_X_MASK to filter MODE flags and set own, known flags:
  spi->flags &= ~SPI_MODE_X_MASK;
  spi->flags |= SPI_MODE_0;

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20201027095724.18654-2-o.rempel@pengutronix.de


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