spi: dw: Add support for Intel Keem Bay SPI

Add support for Intel Keem Bay SPI controller, which uses DesignWare
DWC_ssi core. Bit 31 of CTRLR0 register is added for Keem Bay, to
configure the device as a master or as a slave serial peripheral.

Signed-off-by: Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200505130618.554-6-wan.ahmad.zainie.wan.mohamad@intel.com


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