regulator: Fix default constraints for fixed voltage regulators

Default voltage constraints were being provided for fixed voltage
regulator where board constraints were not provided but these constraints
used INT_MIN as the default minimum voltage which is not a valid value
since it is less than zero. Use 1uV instead.

Also set the default values we set in the constraints themselves since
otherwise the max_uV constraint we determine will not be stored in the
actual constraint strucutre and will therefore not be used.

Signed-off-by: Mark Brown <[e-mail]>
Signed-off-by: Liam Girdwood <[e-mail]>

drivers/regulator/core.c

···
 		int	cmin = constraints->min_uV;
 		int	cmax = constraints->max_uV;
 
-		/* it's safe to autoconfigure fixed-voltage supplies */
+		/* it's safe to autoconfigure fixed-voltage supplies
+		   and the constraints are used by list_voltage. */
 		if (count == 1 && !cmin) {
-			cmin = INT_MIN;
+			cmin = 1;
 			cmax = INT_MAX;
+			constraints->min_uV = cmin;
+			constraints->max_uV = cmax;
 		}
 
 		/* voltage constraints are optional */