mfd: Kconfig: Compile MFD_STW481X with COMPILE_TEST

The driver depends on ARCH_NOMADIK but there isn't a build dependency
so it's a good idea to allow the driver to always be built when the
COMPILE_TEST option is enabled.

That way, the driver can be built with a config generated by make
allyesconfig and check if a patch would break the build.
Signed-off-by: NLuis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/Kconfig

@@ -1482,7 +1482,7 @@ config MFD_WM8994
 
 config MFD_STW481X
 	tristate "Support for ST Microelectronics STw481x"
-	depends on I2C && ARCH_NOMADIK
+	depends on I2C && (ARCH_NOMADIK || COMPILE_TEST)
 	select REGMAP_I2C
 	select MFD_CORE
 	help