ath79: mikrotik: fix build error with kernel 6.1

drivers/mfd/rb4xx-cpld.c:167:19: error: initialization of 'void (*)(struct spi_device *)' from incompatible pointer type 'int (*)(struct spi_device *)' [-Werror=incompatible-pointer-types]
  167 |         .remove = rb4xx_cpld_remove,
      |                   ^~~~~~~~~~~~~~~~~
drivers/mfd/rb4xx-cpld.c:167:19: note: (near initialization for 'rb4xx_cpld_driver.remove')
cc1: some warnings being treated as errors
make[8]: *** [scripts/Makefile.build:250: drivers/mfd/rb4xx-cpld.o] Error 1
make[7]: *** [scripts/Makefile.build:500: drivers/mfd] Error 2
make[6]: *** [scripts/Makefile.build:500: drivers] Error 2
make[5]: *** [Makefile:2012: .] Error 2

As the allocated function does nothing, simply delete it.

Signed-off-by: Koen Vandeputte <[email protected]>

target/linux/ath79/files/drivers/mfd/rb4xx-cpld.c

@@ -151,11 +151,6 @@ static int rb4xx_cpld_probe(struct spi_device *spi)
 				    NULL, 0, NULL);
 }
 
-static int rb4xx_cpld_remove(struct spi_device *spi)
-{
-	return 0;
-}
-
 static const struct of_device_id rb4xx_cpld_dt_match[] = {
 	{ .compatible = "mikrotik,rb4xx-cpld", },
 	{ },
@@ -164,7 +159,6 @@ MODULE_DEVICE_TABLE(of, rb4xx_cpld_dt_match);
 
 static struct spi_driver rb4xx_cpld_driver = {
 	.probe = rb4xx_cpld_probe,
-	.remove = rb4xx_cpld_remove,
 	.driver = {
 		.name = "rb4xx-cpld",
 		.bus = &spi_bus_type,