Revert "mfd: sec-core: Prepare regulators for suspend state to reduce power-consumption"

This reverts commit b7cde707
("mfd: sec-core: Prepare regulators for suspend state to reduce power-consumption")

Commit b7cde707 called regulator_suspend_prepare() to prepare the
regulators for a suspend state. But it did from the device pm suspend
handler while the regulator suspend prepare function iterates over all
regulators and not only the one managed by this device so it doesn't
seems to be correct to call it from within a device driver.

It is better to call the regulator suspend prepare/finish functions
from platform code instead so this patch reverts the mentioned commit.

Suggested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>