regulator: ab8500-ext: Constify ab8500_ext_regulator_ops

ab8500_ext_regulator_ops never need to be modified, make it const so
compiler can put it to .rodata.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/ab8500-ext.c

@@ -718,7 +718,7 @@ static int ab8500_ext_list_voltage(struct regulator_dev *rdev,
 	return -EINVAL;
 }
 
-static struct regulator_ops ab8500_ext_regulator_ops = {
+static const struct regulator_ops ab8500_ext_regulator_ops = {
 	.enable			= ab8500_ext_regulator_enable,
 	.disable		= ab8500_ext_regulator_disable,
 	.is_enabled		= ab8500_ext_regulator_is_enabled,