mfd: tps65218: Introduce dependency on CONFIG_OF

Currently the driver boots only via device tree hence add a
dependency on CONFIG_OF. This leaves with a bunch of unused code
so clean that up.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index c5bc48a..5fecee6 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1413,7 +1413,7 @@
 
 config MFD_TPS65218
 	tristate "TI TPS65218 Power Management chips"
-	depends on I2C
+	depends on I2C && OF
 	select MFD_CORE
 	select REGMAP_I2C
 	select REGMAP_IRQ