regulator: s5m8767: Fix carried over ena_gpio assignment

During registration of regulators if external control for regulator was
set in DTS the ena_gpio and ena_gpio_flags fields of regulator_config
were set to proper values.

However the same regulator_config was used in next iterations of loop so
the ena_gpio fields carried over to next regulators.

The issue was not observed as ena_gpio is supported only for Buck9
regulator which is often the last regulator parsed from DTS.
Be sure to clear ena_gpio config fields before registering the
regulator.

Fixes: ee1e0994

 (regulator: s5m8767: Use GPIO for controlling Buck9/eMMC)
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>