power: regulator: Add support for gpio regulators

Add support for gpio regulators. As of now this driver caters
to gpio regulators with one gpio. Supports setting voltage values to gpio
regulators and retrieving the values.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/power/regulator/Kconfig b/drivers/power/regulator/Kconfig
index c7e88c0..255eccf 100644
--- a/drivers/power/regulator/Kconfig
+++ b/drivers/power/regulator/Kconfig
@@ -68,6 +68,14 @@
 	features for fixed value regulators. The driver implements get/set api
 	for enable and get only for voltage value.
 
+config DM_REGULATOR_GPIO
+	bool "Enable Driver Model for GPIO REGULATOR"
+	depends on DM_REGULATOR
+	---help---
+	This config enables implementation of driver-model regulator uclass
+	features for gpio regulators. The driver implements get/set for
+	voltage value.
+
 config REGULATOR_RK808
 	bool "Enable driver for RK808 regulators"
 	depends on DM_REGULATOR && PMIC_RK808