regulator: provide a helper for registering a fixed regulator

Some devices require a regulator to work, but boards may not have
a software controllable regulator for this device. Provide a helper
function to make it simpler for these boards to register a fixed
regulator as a dummy regulator.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/linux/regulator/fixed.h b/include/linux/regulator/fixed.h
index ffd7d50..936a7d8 100644
--- a/include/linux/regulator/fixed.h
+++ b/include/linux/regulator/fixed.h
@@ -48,4 +48,17 @@
 	struct regulator_init_data *init_data;
 };
 
+struct regulator_consumer_supply;
+
+#if IS_ENABLED(CONFIG_REGULATOR)
+struct platform_device *regulator_register_fixed(int id,
+		struct regulator_consumer_supply *supplies, int num_supplies);
+#else
+static inline struct platform_device *regulator_register_fixed(int id,
+		struct regulator_consumer_supply *supplies, int num_supplies)
+{
+	return NULL;
+}
+#endif
+
 #endif