regulator: core: Replace direct ops->enable usage

There are some direct ops->enable in the regulator core driver. This is
a potential issue as the function _regulator_do_enable() handles gpio
regulators and the normal ops->enable calls. These gpio regulators are
simply ignored when ops->enable is called directly.

One possible bug is that boot-on and always-on gpio regulators are not
enabled on registration.

This patch replaces all ops->enable calls by _regulator_do_enable.

[Handle missing enable operations -- broonie]

Cc: <stable@vger.kernel.org> # 3.10+
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

regulator: Handle invalid enable operation for always/boot on regulators

Signed-off-by: Mark Brown <broonie@linaro.org>