regulator: Fix unbalanced disables/enables in regulator_bulk_{enable,disable} error path

Currently it is possible for regulator_bulk_{enable,disable} operations to
generate unbalanced regulator_{disable,enable} calls in its error path.
In case of an error only those regulators of the bulk operation which actually
had been enabled/disabled should get their original state restored.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>