UPSTREAM: regulator: pwm: Switch to the atomic PWM API

UPSTREAM: regulator: pwm: Switch to the atomic PWM API

Use the atomic API wherever appropriate and get rid of pwm_apply_args()
call (the reference period and polarity are now explicitly set when
calling pwm_apply_state()).

We also make use of the pwm_set_relative_duty_cycle() helper to ease
relative to absolute duty_cycle conversion.

Note that changes introduced by commit fd786fb0276a ("regulator: pwm:
Try to avoid voltage error in duty cycle calculation") are no longer
needed because pwm_set_relative_duty_cycle() takes care of all rounding
approximation for us.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
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 3f4eb39be9b1402ea01a5c67441d0b0bcb74b4b2)

Change-Id: Id12d4d625fb6e1e5ff3725737cc9232e4df40c36
Signed-off-by: David Wu <david.wu@rock-chips.com>