UPSTREAM: regulator: pwm: Properly initialize the ->state field

UPSTREAM: regulator: pwm: Properly initialize the ->state field

The ->state field is currently initialized to 0, thus referencing the
voltage selector at index 0, which might not reflect the current
voltage value.
If possible, retrieve the current voltage selector from the PWM state,
else return -EINVAL.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Brian Norris <briannorris@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit 87248991a1de28e73dc30057e82d831bc11cdd44)

Change-Id: I179395dc7bad7aa867e68c92be7ce92b03ae7112
Signed-off-by: David Wu <david.wu@rock-chips.com>