gpio: xilinx: Correct kernel doc for xgpio_probe()

Kernel doc validator complains:

.../gpio-xilinx.c:556: warning: expecting prototype for xgpio_of_probe(). Prototype was for xgpio_probe() instead

Correct as suggested by changing the name of the function in the doc..

Fixes: 749564ff ("gpio/xilinx: Convert the driver to platform device interface")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Neeli Srinivas <sneeli@xilinx.com>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>