spi: spi-cadence: add support for chip select high

The spi cadence driver should support spi-cs-high in mode bits
so that the peripherals that needs the chip select to be high active can
use it. Add the SPI-CS-HIGH flag in the supported mode bits.

Signed-off-by: Shreyas Joshi <shreyas.joshi@biamp.com>
Link: https://lore.kernel.org/r/20200710211655.1564-1-shreyas.joshi@biamp.com


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