spi: xilinx: Add necessary inclusion and forward declaration

xilinx_spi.h is mnissing inclusion and forward declaration, add them.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Link: https://msgid.link/r/20240308162920.46816-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

include/linux/spi/xilinx_spi.h

@@ -2,6 +2,10 @@
 #ifndef __LINUX_SPI_XILINX_SPI_H
 #define __LINUX_SPI_XILINX_SPI_H
 
+#include <linux/types.h>
+
+struct spi_board_info;
+
 /**
  * struct xspi_platform_data - Platform data of the Xilinx SPI driver
  * @num_chipselect:	Number of chip select by the IP.