fpga: xilinx-spi: Add missing spi_device_id table

fpga: xilinx-spi: Add missing spi_device_id table

The "xlnx,fpga-slave-serial" devicetree compatible string currently misses
its SPI device ID entry. Without an spi_device_id table, the driver still
works with device tree, but triggers the following runtime warning when
registered via SPI core:

SPI driver xlnx-slave-spi has no spi_device_id for xlnx,fpga-slave-serial

Fix it by adding a corresponding spi_device_id table entry.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20251026110237.986279-1-festevam@gmail.com
[ Yilun: Remove extra whitespaces ]
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>