regulator: tps65218: Add OF dependency

This is a DT-only driver, so make it depend on OF and remove of_match_ptr in
the code.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index b05da880..b7c95e8 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -515,7 +515,7 @@
 
 config REGULATOR_TPS65218
 	tristate "TI TPS65218 Power regulators"
-	depends on MFD_TPS65218
+	depends on MFD_TPS65218 && OF
 	help
 	  This driver supports TPS65218 voltage regulator chips. TPS65218
 	  provides six step-down converters and one general-purpose LDO