UPSTREAM: clk: pwm: Use pwm_get_args() where appropriate

UPSTREAM: clk: pwm: Use pwm_get_args() where appropriate

The PWM framework has clarified the concept of reference PWM config (the
platform dependent config retrieved from the DT or the PWM lookup table)
and real PWM state.

Use pwm_get_args() when the PWM user wants to retrieve this reference
config and not the current state.

This is part of the rework allowing the PWM framework to support
hardware readout and expose real PWM state even when the PWM has just
been requested (before the user calls pwm_config/enable/disable()).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit dd0b38b7ca0d8c8aadcf8a17d7c90d36ab8ab6e4)

Change-Id: I54c4b3853359b5fa41f8f949b504f82c6f069034
Signed-off-by: Zhangbin Tong <zebulun.tong@rock-chips.com>