Since commit 00e7e698 ("backlight: pwm_bl: Configure pwm only once
per backlight toggle") calling pwm_backlight_power_off() doesn't disable
the PWM any more. However this is necessary to suspend because PWM
drivers usually refuse to suspend if they are still enabled.

Also adapt shutdown and remove callbacks to disable the PWM for similar
reasons.

Fixes: 00e7e698 ("backlight: pwm_bl: Configure pwm only once per backlight toggle")
Reported-by: Aisheng Dong <aisheng.dong@nxp.com>
Tested-by: Aisheng Dong <aisheng.dong@nxp.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20231009093223.227286-1-u.kleine-koenig@pengutronix.deSigned-off-by: Lee Jones <lee@kernel.org>