spi: xilinx: Fix kernel documentation in the xilinx_spi.h

spi: xilinx: Fix kernel documentation in the xilinx_spi.h

While updating the data structure layout the kernel documentation
became outdated. Synchronize kernel documentation with the actual
data structure layout.

Fixes: 1dd46599f83a ("spi: xilinx: add force_irq for QSPI mode")
Fixes: 082339bc63cc ("spi: spi-xilinx: Add run run-time endian detection")
Reviewed-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240308162920.46816-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>