regulator: Set ena_gpio_initialized in regulator drivers

This patch sets ena_gpio_initialized for all drivers which set a
ena_gpio from parsed DT properties. Drivers using pdata may get zero
initialized pdata and therefore copy a 0 into the regulator_config
ena_gpio field.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>