kernel: add missing dependency to regmap to kmod-gpio-mcp23s08

This fixes a build problem recently introduced.

Fixes: a904003b9b ("kernel: fix kmod-gpio-mcp23s08 for linux 4.14")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/kernel/linux/modules/other.mk

@@ -227,7 +227,7 @@ $(eval $(call KernelPackage,gpio-dev))
 define KernelPackage/gpio-mcp23s08
   SUBMENU:=$(OTHER_MENU)
   TITLE:=Microchip MCP23xxx I/O expander
-  DEPENDS:=@GPIO_SUPPORT +kmod-i2c-core
+  DEPENDS:=@GPIO_SUPPORT +kmod-i2c-core +LINUX_4_14:kmod-regmap
   KCONFIG:= \
 	CONFIG_GPIO_MCP23S08 \
 	CONFIG_PINCTRL_MCP23S08