spi: dw-pci: Fix Chip Select amount on Intel Elkhart Lake PSE SPI

Intel(R) Programmable Services Engine (Intel(R) PSE) SPI controllers in
Intel Elkhart Lake have two Chip Select signals instead of one.

Reported-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20191018132131.31608-3-jarkko.nikula@linux.intel.com


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