dm: regulator: add max77686 regulator driver

This commit adds support to MAX77686 regulator driver,
based on a driver model regulator's API. It implements
almost all regulator operations, beside those for setting
and geting the Current value.
For proper bind and operation it requires the MAX77686 PMIC driver.

New file: drivers/power/regulator/max77686.c
New config: CONFIG_DM_REGULATOR_MAX77686

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/power/regulator/Kconfig b/drivers/power/regulator/Kconfig
index cb15162..0cdfabc 100644
--- a/drivers/power/regulator/Kconfig
+++ b/drivers/power/regulator/Kconfig
@@ -15,3 +15,11 @@
 	when binding the regulator devices. The pmic_bind_childs() can be used
 	for this purpose if PMIC I/O driver is implemented or dm_scan_fdt_node()
 	otherwise. Detailed informations can be found in the header file.
+
+config DM_REGULATOR_MAX77686
+	bool "Enable Driver Model for REGULATOR MAX77686"
+	depends on DM_REGULATOR && DM_PMIC_MAX77686
+	---help---
+	This config enables implementation of driver-model regulator uclass
+	features for REGULATOR MAX77686. The driver implements get/set api for:
+	value, enable and mode.