mfd: Make WM8400 depend on I2C until SPI is submitted

Otherwise we could build in WM8400 but not I2C.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@openedhand.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 8aa4333..b550267 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -116,6 +116,7 @@
 
 config MFD_WM8400
 	tristate "Support Wolfson Microelectronics WM8400"
+	depends on I2C
 	help
 	  Support for the Wolfson Microelecronics WM8400 PMIC and audio
 	  CODEC.  This driver adds provides common support for accessing