gpio: mcp230xx: Add support for models with SPI interface.

Signed-off-by: Piotr Wojtaszczyk <piotr.wojtaszczyk@timesys.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 2df3dc4..a7fb1eb 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -256,6 +256,9 @@
 	   - MCP23008
 	   - MCP23017
 	   - MCP23018
+	   - MCP23S08
+	   - MCP23S17
+	   - MCP23S18
 
 config MSCC_SGPIO
 	bool "Microsemi Serial GPIO driver"