regulator: Complain if a voltage range is specified but can't be used

It doesn't make much sense to specify a range of voltages consumers can
use if they haven't been given permission to change the voltage. Log if
this happens, probably the user forgot to specify CHANGE_VOLTAGE.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>

drivers/regulator/core.c

@@ -805,6 +805,11 @@ static void print_constraints(struct regulator_dev *rdev)
 		count += sprintf(buf + count, "standby");
 
 	rdev_info(rdev, "%s\n", buf);
+
+	if ((constraints->min_uV != constraints->max_uV) &&
+	    !(constraints->valid_ops_mask & REGULATOR_CHANGE_VOLTAGE))
+		rdev_warn(rdev,
+			  "Voltage range but no REGULATOR_CHANGE_VOLTAGE\n");
 }
 
 static int machine_constraints_voltage(struct regulator_dev *rdev,