regulator: fixed regulator_bulk_enable unwinding code

Unwinding code disables all successfully enabled regulators.
Error is logged for every failed regulator.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>