power: regulator: Allow PWM regulator to be omitted from SPL.

This patch allows to enable the PWM regulator driver
independent for U-Boot and SPL.

Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/drivers/power/regulator/Kconfig b/drivers/power/regulator/Kconfig
index 09b311d..3ed0dd2 100644
--- a/drivers/power/regulator/Kconfig
+++ b/drivers/power/regulator/Kconfig
@@ -61,6 +61,13 @@
 	This driver is controlled by a device tree node
 	which includes voltage limits.
 
+config SPL_REGULATOR_PWM
+	bool "Enable Driver for PWM regulators in SPL"
+	depends on REGULATOR_PWM
+	help
+	  This config enables implementation of driver-model regulator uclass
+	  features for PWM regulators in SPL.
+
 config DM_REGULATOR_MAX77686
 	bool "Enable Driver Model for REGULATOR MAX77686"
 	depends on DM_REGULATOR && DM_PMIC_MAX77686