The driver was removed but 'make clean' still failed:
scripts/Makefile.clean:17:
[...]/drivers/staging/cs5535_gpio/Makefile: No such file or directory
make[3]: *** No rule to make target
`[...]/drivers/staging/cs5535_gpio/Makefile'.  Stop.
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
 obj-$(CONFIG_VME_BUS)          += vme/
 obj-$(CONFIG_DX_SEP)            += sep/
 obj-$(CONFIG_IIO)              += iio/
-obj-$(CONFIG_CS5535_GPIO)      += cs5535_gpio/
 obj-$(CONFIG_ZRAM)             += zram/
 obj-$(CONFIG_XVMALLOC)         += zram/
 obj-$(CONFIG_ZCACHE)           += zcache/