spi: dw: Remove unused dw_spi_cleanup function

The dw_spi_cleanup() function was removed by commit c63f5da00845
"spi: dw: Don't call kfree for memory allocated by devm_kzalloc".

commit ec37e8e1f0e3 "spi: dw: migrate to generic queue infrastructure" added
dw_spi_cleanup() but never use it. So now I got below build warning:

CC [M] drivers/spi/spi-dw.o
drivers/spi/spi-dw.c:609:13: warning: 'dw_spi_cleanup' defined but not used [-Wunused-function]

Signed-off-by: Axel Lin <[e-mail]>
Acked-by: Baruch Siach <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-dw.c

···
 	return 0;
 }
 
-static void dw_spi_cleanup(struct spi_device *spi)
-{
-	struct chip_data *chip = spi_get_ctldata(spi);
-	kfree(chip);
-}
-
 /* Restart the controller, disable all interrupts, clean rx fifo */
 static void spi_hw_init(struct dw_spi *dws)
 {