pwm: rockchip: Round period/duty down on apply, up on get

pwm: rockchip: Round period/duty down on apply, up on get

With CONFIG_PWM_DEBUG=y, the rockchip PWM driver produces warnings like
this:

  rockchip-pwm fd8b0010.pwm: .apply is supposed to round down
  duty_cycle (requested: 23529/50000, applied: 23542/50000)

This is because the driver chooses ROUND_CLOSEST for purported
idempotency reasons. However, it's possible to keep idempotency while
always rounding down in .apply().

Do this by making .get_state() always round up, and making .apply()
always round down. This is done with u64 maths, and setting both period
and duty to U32_MAX (the biggest the hardware can support) if they would
exceed their 32 bits confines.

Fixes: 12f9ce4a5198 ("pwm: rockchip: Fix period and duty cycle approximation")
Fixes: 1ebb74cf3537 ("pwm: rockchip: Add support for hardware readout")
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Link: https://lore.kernel.org/r/20250616-rockchip-pwm-rounding-fix-v2-1-a9c65acad7b6@collabora.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>