generic: add missing symbol

When compiling with all modules enabled, Kconfig complains about
CONFIG_I2C_DESIGNWARE_SLAVE being unset. Disable this symbol by default.

Fixes commit e9c9b5ec72e4 ("kernel: package Synopsys Designware PCI to I2C controller")

Signed-off-by: David Bauer <[email protected]>

target/linux/generic/config-5.10

@@ -2347,6 +2347,7 @@ CONFIG_HZ_100=y
 # CONFIG_I2C_DEMUX_PINCTRL is not set
 # CONFIG_I2C_DESIGNWARE_PCI is not set
 # CONFIG_I2C_DESIGNWARE_PLATFORM is not set
+# CONFIG_I2C_DESIGNWARE_SLAVE is not set
 # CONFIG_I2C_DIOLAN_U2C is not set
 # CONFIG_I2C_EG20T is not set
 # CONFIG_I2C_ELEKTOR is not set

target/linux/generic/config-5.4

@@ -2101,6 +2101,7 @@ CONFIG_HZ_100=y
 # CONFIG_I2C_DEMUX_PINCTRL is not set
 # CONFIG_I2C_DESIGNWARE_PCI is not set
 # CONFIG_I2C_DESIGNWARE_PLATFORM is not set
+# CONFIG_I2C_DESIGNWARE_SLAVE is not set
 # CONFIG_I2C_DIOLAN_U2C is not set
 # CONFIG_I2C_EG20T is not set
 # CONFIG_I2C_ELEKTOR is not set